Najko JahnLisa MatthiasMikael Laakso Göttingen State and University Library,
University of Göttingen
Platz der Göttinger Sieben 1, 37073 Göttingen, Germany
<EMAIL_ADDRESS>Department of Political Science, John F.
Kennedy Institute, Freie Universität Berlin
Lansstraße 7-9, 14195 Berlin, Germany
<EMAIL_ADDRESS>Information Systems Science, Hanken School of Economics
Arkadiankatu 22, 00100 Helsinki, Finland
<EMAIL_ADDRESS>Correspondence concerning this article should be
addressed to Najko Jahn

# Transparency to hybrid open access through publisher-provided metadata: An
article-level study of Elsevier

###### Abstract

With the growth of open access (OA), the financial flows in scholarly journal
publishing have become increasingly complex, but comprehensive data and
transparency into these flows are still lacking. The opaqueness is especially
concerning for hybrid OA, where subscription-based journals publish individual
articles as OA if an optional fee is paid. This study addresses the lack of
transparency by leveraging Elsevier article metadata and provides the first
publisher-level study of hybrid OA uptake and invoicing. Our results show that
Elsevier’s hybrid OA uptake has grown steadily but slowly from 2015-2019,
doubling the number of hybrid OA articles published per year and increasing
the share of OA articles in Elsevier’s hybrid journals from 2.6% to 3.7% of
all articles. Further, we find that most hybrid OA articles were invoiced
directly to authors, followed by articles invoiced through agreements with
research funders, institutions, or consortia, with only a few funding bodies
driving hybrid OA uptake. As such, our findings point to the role of
publishing agreements and OA policies in hybrid OA publishing. Our results
further demonstrate the value of publisher-provided metadata improve the
transparency in scholarly publishing by linking invoicing data to
bibliometrics.

##  1 Introduction

The rise of open access (OA) has added complexity to scholarly publishing,
particularly concerning transparency of economic dimensions. Financial
transparency in journal publishing has long been lacking because Big Deal
subscription contracts between academic institutions and large academic
publishers usually include confidentiality clauses that prohibit publicly
sharing the scope or pricing of such agreements (Bergstrom et al., 2014;
Frazier, 2001; Larivière et al., 2015). Further, the distributed payment
processes to access and publish scholarly articles add to the opacity of the
financial flows of scholarly publishing (Lawson et al., 2016) as they can
involve several actors simultaneously, including authors, research
institutions, libraries, and funders.

The problem with this lack of transparency becomes more apparent in the case
of hybrid OA. In this OA business model, individual articles can be made
openly available by paying an article processing charge (APC), while the
journal as a whole remains subscription-access. Hence, hybrid OA was
originally introduced as a low-risk transitional model that allows journals to
gradually convert to full OA and reduce subscription costs as the OA uptake
increases (Prosser, 2003). Many large subscription publishers have since
incorporated hybrid OA, but there have been concerns that the hybrid model
allows for double dipping—receiving two payments for one article, the APC and
subscription fees (Prosser, 2015; Shieber, 2009). While publishers assure they
adjust their pricing (Mittermaier, 2015), without transparency around the
uptake of hybrid OA and both revenue streams, such claims are impossible to
evaluate. This is especially concerning because hybrid OA has recently gained
popularity after a decade of only slow uptake (Björk, 2012). The main drivers
of this development have been research institutions and funders that
implemented OA policies, allocated OA funds, and established formal agreements
with publishers that allow affiliated authors to publish OA free-of-charge
(Laakso & Björk, 2016).

With the recent introduction of transformative agreements, an evolving concept
describing contracts that shift library spending from subscriptions to OA
(Borrego et al., 2020; Hinchliffe, 2019), the demand for publisher-provided
data has increased. More transparency about hybrid OA uptake and funding could
facilitate the assessment and adjustment of publisher contracts (Schimmer et
al., 2015), enhance OA mandate compliance monitoring, and avoid double-dipping
(Larivière & Sugimoto, 2018). However, previous studies have noted an absence
of transparency in hybrid OA publishing and a considerable lack of publicly
available and standardized data (Laakso & Björk, 2016; Lawson, 2015; Pinfield
et al., 2016)

This paper investigates to what extent publisher-provided data can increase
the transparency around hybrid OA by taking Elsevier, the largest scholarly
journal publisher (Larivière et al., 2015), as the starting point for an
empirical analysis of hybrid OA uptake and invoicing. Our approach is based on
openly available data sources and combines scholarly metadata from Crossref, a
DOI registration agency, with APC invoicing data from Elsevier. The compiled
data enable us to analyze the hybrid OA uptake in Elsevier journals between
2015 and 2019 by license and subject, and to compare it with Elsevier’s full
and delayed OA program. Further, we determine whether hybrid APCs were waived
or charged to authors or as part of publishing agreements. In the latter case,
we examine the invoiced academic consortia and research funders. As such, our
findings have implications for research and OA policy and highlight the
potential of publisher-provided data for large-scale, instantaneous analysis
of hybrid OA uptake and invoicing.

##  2 Background

###  2.1 Prevalence and uptake studies

In the first article-level study on hybrid OA, Laakso & Björk (2016) reported
that between 2007 and 2013, the five largest publishers–Elsevier, Sage,
Springer, Taylor & Francis, and Wiley–recorded growing numbers of hybrid
journals that coincided with a twenty-fold increase in hybrid OA (from 666 to
13,994). As a result, hybrid journals with at least one OA article more than
doubled in number (1,082 in 2009, 2,714 in 2013) but fell by 31% relative to
the total number of hybrid journals. Laakso and Björk’s (2016) exploratory
approach yielded a comprehensive overview tracking the growth of hybrid OA
over time and across multiple publishers, but due to the amount of manual data
collection and cleaning it is unsuitable for repeated use. Minimizing such
manual tasks, Nelson & Eggett (2017) narrowed their focus to one publisher–the
American Chemical Society (ACS)–and requested a list of all hybrid OA articles
published from 2006-2011 from the ACS. To assess the hybrid OA uptake, the
authors aggregated and compared the number of OA (n=814) and subscription
articles (n=27,621), finding that over the five years, 2.9% of ACS articles
were published as hybrid OA.

Contrary to the previous two studies, Kirkman (2018) took a research funder as
a starting point, reporting a 26% share of hybrid OA for articles funded by
the Australian National Health and Medical Research Council from 2012-2014
(816 of 3,190). Kirkman collected research articles using the Funding Agency
and Funding Text search fields on Web of Science, and classified articles as
OA when they were freely available on the publisher website, and further
distinguished hybrid OA articles based on journal-level information from the
publisher website, such as hybrid OA journal and APC lists. Another approach
is presented by Pölönen et al. (2020), who used current research information
system (CRIS) data—institutional publication data—to study the extent of OA
among Finnish research publications from 2016-2017 (n=34,507 research
articles). As part of the analysis, the authors identified hybrid OA articles
through a dedicated OA status metadata field that has been mandatory to report
in Finland since 2016 and found a 7% share of hybrid OA. However, the
drawbacks of Kirkman’s (2018) and Pölönen et al.’s (2020) approaches are that
such data sources might not be openly available or, regarding CRIS data, might
not be available at all because not all countries maintain comprehensive
institutional publication data.

Other studies assessed the share of (hybrid) OA for the entire corpus of
research articles. Using DOI-assigned research articles indexed in the Web of
Science Core Collection (n=2,610,305) as a benchmark, Martín-Martín et al.
(2018) investigated how many research articles from 2009 and 2014 are freely
available through Google Scholar. After identifying OA articles through
licensing information from Crossref, the authors estimated the share of hybrid
OA at around 0.5% in 2009 and 1.5% in 2014. Similarly, in a study assessing
the OA level among all scholarly articles and that experienced by Unpaywall
users, Piwowar et al. (2018) obtained license information through Crossref and
web-scraping. The study found 3.6% of 100,000 random Crossref DOIs were hybrid
OA and pointed towards a growing trend in recent years that recorded a hybrid
OA share of 9.4% of all articles published in 2015.

Since its launch, Unpaywall has become widely used in bibliometric research
and rankings (Huang et al., 2020; Robinson-Garcia et al., 2020). However, the
lack of standardized and comprehensive publisher-provided data has required
several updates to Unpaywall to improve hybrid OA identification and
differentiation from delayed OA (Piwowar et al., 2019; Unpaywall, n.d.-b;
Unpaywall, n.d.-c), illustrating ongoing challenges in tracking and comparing
hybrid OA prevalence over time.

###  2.2 Financial studies

Pinfield et al.’s (2016) analysis of APC payment records provided by 23 United
Kingdom (UK) higher education institutions revealed a sharp increase in
central payments from 2007-2013, which was largely attributed to the
introduction of block grants by Research Councils UK (RCUK) and non-compliance
sanctions by the Wellcome Trust. Moreover, the study showed that OA fees were
paid almost exclusively through block grants (92%), and only a small number of
APCs were paid through internal funding (7%). In contrast, a recent Springer
Nature survey found that authors draw on a range of funding sources to cover
OA fees, such as dedicated institutional OA funds, block grants, OA
agreements, or research grants (Monaghan et al., 2020). Most hybrid OA authors
were supported through dedicated institutional OA funds (43%, excluding block
grants) and OA agreements with Springer Nature (34%). The differences between
these two studies might be due to different policy and funding
arrangements—considering the introduction of OA agreements since Pinfield et
al. (2016) and Monaghan et al.’s (2020) more regionally diverse sample.

Regional and policy differences in APC payments also came to light in a study
by Jahn & Tullney (2016) that analyzed APC records from 30 German higher
education and research institutions, the Austrian Science Fund (FWF), Jisc,
and the Wellcome Trust. In particular, the study revealed large differences in
the amount of hybrid OA funded from 2014-2015. Whilst hybrid OA accounted for
less than 1% of APCs paid by German institutions (23 of 3,846), the three non-
German research funders recorded a hybrid share of 75% (11,533 of 15,779).
According to Jahn & Tullney (2016), this could point towards differences in
science policy, such as hybrid OA being supported by the three non-German
research funders but not by Germany’s largest national funder, the German
Research Foundation (DFG). Another possibility is that German hybrid OA fees
were paid from budgets not reported to the Open APC initiative, a crowd-
sourcing effort (Pieper & Broschinski, 2018) from where the authors acquired
data. Among these unreported funds are research grants and research unit
budgets, which author surveys identified as APC funding sources (Graaf, 2017;
Monaghan et al., 2020). As such, Jahn and Tullney’s (2016) findings could
reflect the complexities and potential limitations of institutional OA
spending data that Pinfield et al. (2016) and Monaghan et al. (2020)
attributed to incomplete or missing records.

In recent years, national consortia in Europe negotiated publishing agreements
covering hybrid OA fees for affiliated authors (Borrego et al., 2020). While
these improved invoicing workflows, internal assessments of hybrid OA uptake
and invoicing remain challenging because transparent and comparative data have
largely remained absent (Marques & Stone 2020). Such publicly available
information might be scarce because publishers lack or withhold such data, or
due to confidentiality clauses (Marques & Stone 2020; Marques et al., 2019;
Monaghan et al., 2020).

###  2.3 Research questions and aims

In this paper, we focus on Elsevier, a prominent example in recent hybrid OA
uptake and financial studies (Laakso & Björk 2016; Pinfield et al. 2016).
Elsevier’s OA portfolio presents the challenges in examining hybrid OA
described above. For instance, distinguishing between different OA types.
Elsevier supports delayed (Elsevier, n.d.-b), hybrid, and full OA, including
so-called mirror journals—full OA counterparts of hybrid journals addressing
OA policies opposed to hybrid OA (Harrison, 2019). Further, Elsevier processes
APC invoices through various channels, such as agreements with research
funders and library consortia or, in the absence thereof, the authors
(Elsevier, n.d.-a, n.d.-c). Surprisingly, we found Elsevier article-level
metadata embedded in XML full-texts indicating the articles’ OA status and
invoicing. Leveraging this publicly available data, we address the lack of
transparency around hybrid OA noted in previous studies. In particular, we use
this novel approach to answer the following questions:

  * •

What was the uptake of Elsevier’s hybrid OA publishing option between 2015 and
2019?

  * •

Through which channels were hybrid APCs invoiced, and who were the recipients?

##  3 Methodology

For this study, we collected data relating to Elsevier’s hybrid OA option by
drawing on multiple freely available data sources. We identified Elsevier
hybrid journals through Elsevier’s APC list and supplemented our sample with
Crossref metadata and text-mined invoicing data to investigate the invoicing
of immediate OA articles provided under a Creative Commons (CC) license in
subscription-based journals. Figure 1 visualizes the automated workflow we
used to collect data from Elsevier and Crossref.

Figure 1: Data Collection Workflow to Obtain Article-Level OA and Invoicing
Data.

First, we identified hybrid journals through an Elsevier APC price list from
May 2020 provided by Matthias (2020). We excluded journals that transitioned
from hybrid to full OA and reverse-flip journals that flipped from full to
hybrid OA (Matthias et al., 2019). Overall, we identified 1,970 unique hybrid
journals that published between 2015 and 2019.

Next, we used an openly available Crossref database snapshot (Crossref, 2020),
which contains all Crossref records registered until March 2020, to calculate
the journals’ combined article volume for the five-year period from 2015-2019.
We only included articles published in regular issues aside from supplements
containing conference contributions like meeting abstracts, indicated by non-
numeric pagination. We excluded non-scholarly journal content, such as the
table of contents, following Unpaywall’s paratext recognition approach
(Unpaywall, n.d.-a), which we expanded to include patterns indicating
corrections. Furthermore, we categorized the articles by subject according to
the All Science Journal Classification code (ASJC) and added citation
indicators from the Scopus Source Title list (version June 2020) based on the
journal they were published in.

We identified OA articles through CC licenses in Crossref metadata records
(Hendricks et al., 2020) and then downloaded the XML version of all CC-
licensed articles published in a hybrid journal. From the XML files, we
obtained the articles’ OA status and invoicing information (see Table 1). We
determined whether articles were immediate or delayed OA using the XML node
openArchiveArticle and measured the uptake of hybrid OA. Moreover, we obtained
the invoice channels and recipients of hybrid OA APCs. Using the
openaccessSponsorType node, we distinguished between four invoice channels,
including invoices billed to authors, as part of publishing agreements with
funding bodies (cf. Elsevier (n.d.-a)), exempted through fee waivers (e.g., in
“cases of genuine need” or due to society or university sponsorships, cf.
Elsevier, n.d.-c), and other types not specified by Elsevier. Finally, when
hybrid APCs were invoiced as part of agreements, we identified invoice
recipients through the openaccessSponsorName node.

Table 1: Metadata in Elsevier XML Full-Texts. XML node |  Description
---|---
openaccessArticle |  Was the article open access?
openaccessSponsorType |  Invoice channel.
openaccessSponsorName |  Invoice recipient.
openArchiveArticle |  Was open access provided through Elsevier’s Open Archive program?

We manually classified invoice recipients based on their institutional
sectors, countries, and primary research areas. Following the OECD’s Frascati
Manual (OECD, 2015, p. 91), we coded for four sectors: business enterprise,
government, higher education, and private non-profit. Due to the low article
volume, we combined the business enterprise sector with invoice recipients
Elsevier listed as “authors” and “third-party sponsor” into “Others”.
Moreover, we categorized invoice recipients according to the countries
representing their scope of funding and based on the following primary
research areas health sciences, life sciences, physical sciences and
mathematics, social sciences and humanities, broad (i.e., multiple research
areas), and unknown. Further, we compared Elsevier’s invoicing data with
institutional spending data from the Open APC initiative.

Throughout this mostly automated data gathering and analysis process, we used
tools from the Tidyverse (Wickham et al., 2019) for the R programming language
(R Core Team, 2020). To allow for efficient data manipulation and retrieval,
we imported the Crossref dump to Google BigQuery, applying the rcrossref
(Chamberlain et al., 2020) parsers to extract relevant metadata fields. We
used crminer (Chamberlain, 2020) to obtain the XML-full texts from Elsevier.

## Results

This section first presents the results of our analysis of hybrid OA uptake in
Elsevier’s journal portfolio with a view to licensing, disciplinary
differences, and citation impact. Then, we present a descriptive analysis of
Elsevier’s invoicing data, highlighting licensing and disciplinary differences
for invoicing channels and invoice recipients.

### Uptake of Hybrid Open Access

#### Overview

Between 2015 and 2019, 1,755 of 1,970 (89.1%) hybrid journals published at
least one OA article. Together these journals published 71,643 OA articles,
which represented 3% of their total article volume (n=2,422,087). Table 2
presents findings for each year and the aggregated five-year period,
illustrating moderate growth of hybrid OA over time. Each year, the number of
hybrid journals with at least one OA article increased, as did the number of
immediate OA articles in these journals, which nearly doubled from 10,672 in
2015 to 19,311 in 2019. However, since the journals’ total article output also
grew over time, the relative share of OA articles in hybrid journals only
increased slightly from 2.6% to 3.7%.

Table 2: Elsevier Hybrid OA Uptake 2015-2019. | 2015 | 2016 | 2017 | 2018 | 2019 | 2015-19
---|---|---|---|---|---|---
Elsevier Hybrid Journals with ≥ 1 OA article
Total | 1,317 | 1,364 | 1,401 | 1,501 | 1,600 | 1,755
Articles in Elsevier Hybrid Journals with ≥ 1 OA Article
Total | 406,701 | 422,423 | 436,418 | 468,952 | 518,062 | 2,422,087
Avg. | 308.8 | 309.7 | 311.5 | 312.4 | 323.8 | 1,380.1
SD | 401.1 | 419.6 | 427.5 | 445.6 | 479.9 | 1,937.5
OA Articles in Elsevier Hybrid Journals with ≥ 1 OA Article
Total | 10,672 | 12,729 | 13,361 | 15,570 | 19,311 | 71,643
Avg. | 8.1 | 9.3 | 9.5 | 10.4 | 12.1 | 40.8
SD | 12.9 | 19.7 | 15.6 | 16.2 | 20.1 | 68.9
OA Uptake in Elsevier Hybrid Journals with ≥ 1 OA Article
Total (%) | 2.6 | 3.0 | 3.1 | 3.3 | 3.7 | 3.0
Avg. | 3.7 | 4.3 | 4.4 | 4.7 | 5.4 | 3.8
SD | 4.5 | 5.9 | 5.1 | 4.9 | 5.7 | 4.1

Figure 2 presents a box-and-whiskers plot of the OA uptake in Elsevier hybrid
journals by year, showing variation among the journals. Notably, the upper
quartiles and whiskers stretch farther over the years, which indicates that
the range of uptake among journals with an above-average proportion of OA
articles increased over the years. Nevertheless, the prevalence of hybrid OA
remained relatively low; in 2019, 95% of Elsevier hybrid journals published
≤15.6% of their articles OA.

Figure 2: Open Access Uptake per Elsevier Hybrid Journal (Per Year).

Note: The Y-axis is limited to an OA share of 20%.

During the same period, Elsevier provided OA to 328,601 articles in total
(i.e., full, hybrid, and delayed OA combined), representing 12.4% of the total
article volume (n=2,643,474). Looking at Figure 3, it is apparent that the OA
article volume of hybrid journals (n=71,643; 21.8%) lagged behind delayed OA
(n=163,643; 49.8%) and full OA journals (n=93,315; 28.4%), which included 817
articles published in 38 mirror journals.

Figure 3: Elsevier OA Article Volume 2015-2019 by (A) OA Type and (B) Open
Content License.

#### License Prevalence

As far as we observed, OA articles in Elsevier hybrid journals were published
under two possible CC licenses–CC BY or CC BY-NC-ND. CC BY allows others to
distribute, remix, adapt, and build upon the licensed work, including for
commercial purposes, as long as the original author is credited. In contrast,
CC BY-NC-ND is less permissive as it prohibits commercial reuse and
derivatives. From 2015-2019, the proportion of hybrid OA articles published
under a CC BY-NC-ND license marginally increased and maintained a greater
share than CC BY (see Figure 3-B). Interestingly, Figure 3-B also reveals that
nevertheless hybrid journals had the highest number and proportion of OA
articles licensed under CC BY (n=29,752; 41.5%) compared to full OA journals
(n=17,293; 18.5%) and Elsevier’s delayed OA program (n=1,568; 1%). Most
delayed OA articles were provided under an Elsevier user license (Els-User),
which prohibits reuse for commercial purposes.

#### Subject Area and Field

Next, we present the hybrid OA uptake of different disciplines. Table 3
presents the high-level findings by ASJC subject area. Between 2015 and 2019,
the physical sciences (712 hybrid journals; 29,584 OA articles) and health
sciences (634 hybrid journals; 25,119 OA articles) recorded the most hybrid
journals with at least one OA article. However, the life sciences (538 hybrid
journals; 31,383 OA articles) published the most hybrid OA articles, while the
social sciences published the least (372 hybrid journals; 11,204 articles). It
is important to note, though, that there is a large overlap between the
journals’ subject areas. Therefore, Table 3 also assigns hybrid journals and
OA articles fractionally, where journals assigned more than one ASJC subject
were counted once for each. For the remaining results, we only present the
full counting.

Table 3: Full and Fractional Counting of Subject Areas (2015-2019).

| Full counting | Fractional counting
---|---|---
Subject area | Journals | OA articles | Journals | OA articles
Health sciences | 634 | 25,119 | 506.6 | 18,415
Life sciences | 538 | 31,383 | 368.5 | 21,753
Physical sciences | 712 | 29,584 | 584.4 | 23,915
Social sciences | 372 | 11,204 | 283.5 | 7,462

Note: One multidisciplinary journal (61 OA articles) and 11 journals (37 OA
articles) that could not be matched to the Scopus Source Title list to obtain
ASJC codes are not included.

Figure 4 presents the journals’ five-year OA uptake grouped by subject area
and field and in comparison to the overall median (Mdn= 2.5%; excluding one
journal coded as multidisciplinary). The box plot reveals some variation
between the subject areas. Notably, with the exception of environmental
science and earth and planetary sciences, hybrid journals from the physical
sciences show a lower median OA proportion, whereas most life sciences and
social sciences journals ranked above average. Figure X also shows large
variations among the 26 subject fields, with the highest OA rates in
immunology and microbiology (Mdn=5.1%), environmental science (Mdn=4.8%), and
neuroscience (Mdn=4.3%), whilst chemistry (Mdn=1.4%), materials science
(Mdn=1.4%), and dentistry (Mdn=0.6%) recorded the lowest OA rate.

Figure 4: OA Uptake in Elsevier Hybrid Journals by Subject Area and Field
(2015-2019).

Note: Y-axis is limited to an OA share of 20%; the red line represents the
overall median (2.5), jittered dots represent individual journals. Subject
fields are ordered based on the median OA uptake.

#### Citation Impact

Furthermore, we compared the journals’ field-specific citation impact and
their OA uptake. Spearman’s rho correlation coefficient was used to assess the
relationship between the 2019 Source Normalized Impact per Paper (SNIP) value
calculated by Scopus and the journals’ OA uptake that year. Considering only
journals with at least one OA article, we found a weak but positive
correlation between journal impact and OA uptake ($r_{s}$=0.1679, $p<0.001$),
suggesting that the relationship is not very strong, based on our data (see
Figure 5).

Figure 5: SNIP versus OA Uptake in Elsevier Hybrid Journals 2019.

### Invoicing for Hybrid Open Access

#### Invoice Channels

As can be seen from Table 4, hybrid OA APC were most often invoiced to authors
(n=41,725; 58.2%) and to a lesser extent as part of agreements (n=24,250;
33.8%). Interestingly, we also found a small number of cases where hybrid APCs
were waived (n=4,345; 6.1%).

Table 4: Invoice Channels for Elsevier Hybrid OA Articles (2015-2019). Invoicing channel | Hybrid OA articles (n) | Percentage
---|---|---
Author | 41,725 | 58.2
Agreement | 24,250 | 33.8
Fee waived | 4,345 | 6.1
Other | 1,323 | 1.8
Total | 71,643 | 100.0

Figure 6 illustrates that over the years, Elsevier has increasingly invoiced
authors directly compared to research funders or academic consortia
(“Agreement”). The share of fee-waived articles remained relatively stable,
but we found different types of waivers. Around 51.7% of fee waivers were
linked to a third party. For instance, the French Académie des Sciences,
presumably covering OA publication for 853 OA articles in its society journals
for affiliated authors. The remaining 48.3% of waived articles did not
disclose any invoice recipient. Moreover, Figure 6 compares the invoicing
channels based on CC license variants. When Elsevier invoiced authors
directly, most OA articles in hybrid journals were published under a non-
commercial license (n=32,086; 76.9%), whereas most articles billed as part of
agreements were licensed under the more permissive CC BY license (n=18,331;
75.6%).

Figure 6: Elsevier Hybrid OA Articles by Invoice Channel and CC License (Per
Year).

Note: Grey bars show the total number of hybrid OA articles published in
Elsevier journals.

We also observed large differences in OA invoicing among subject fields. Table
5 shows the number of OA articles by subject field and invoice channel. For
articles in nursing, decision sciences, and pharmacology, toxicology and
pharmaceutics, Elsevier predominantly invoiced authors, whereas most energy
and chemical engineering articles were invoiced through agreements. Likewise,
the majority of articles in materials science, chemistry and physics and
astronomy were not invoiced to authors but facilitated through agreements or
waived. The large share of waived APCs in physics and astronomy can be
attributed to a single 2015 issue of Nuclear and Particle Physics Proceedings.

Table 5: Invoice Channels by Subject (2015-2019).

| Invoice channel (in %)
---|---
Subject | OA articles | Author | Agreement | Fee waived | Other
Nursing | 1,504 | 82 | 16 | 1 | 1
Decision Sciences | 785 | 72 | 27 | 0 | 1
Pharmacology, Toxicology and Pharmaceutics | 4,075 | 69 | 27 | 1 | 2
Business, Management and Accounting | 1,751 | 68 | 29 | 2 | 1
Dentistry | 288 | 68 | 17 | 10 | 5
Health Professions | 674 | 67 | 24 | 3 | 5
Medicine | 23,623 | 65 | 25 | 6 | 4
Agricultural and Biological Sciences | 7,956 | 63 | 31 | 5 | 1
Computer Science | 3,185 | 63 | 36 | 0 | 1
Economics, Econometrics and Finance | 2,071 | 62 | 33 | 5 | 0
Veterinary | 2,091 | 61 | 25 | 13 | 1
Social Sciences | 6,306 | 60 | 36 | 3 | 0
Earth and Planetary Sciences | 4,532 | 59 | 35 | 5 | 0
Biochemistry, Genetics and Molecular Biology | 15,903 | 59 | 35 | 4 | 2
Immunology and Microbiology | 5,542 | 59 | 34 | 6 | 2
Environmental Science | 9,000 | 58 | 38 | 3 | 1
Psychology | 3,087 | 57 | 40 | 2 | 1
Neuroscience | 5,906 | 56 | 40 | 3 | 1
Arts and Humanities | 1,565 | 54 | 44 | 1 | 0
Mathematics | 2,105 | 53 | 38 | 8 | 0
Engineering | 8,405 | 50 | 46 | 3 | 1
Materials Science | 4,838 | 49 | 47 | 4 | 0
Chemistry | 4,033 | 48 | 46 | 5 | 1
Energy | 4,286 | 46 | 52 | 1 | 1
Chemical Engineering | 2,977 | 45 | 47 | 7 | 1
Physics and Astronomy | 5,859 | 40 | 38 | 22 | 0

#### Invoice Recipients

Elsevier’s data offer more insight into OA invoicing. Overall, we identified
63 academic institutions and funders that received invoices as part of
publishing agreements. By a large margin, most invoices were issued to UK-
based research funders and institutions (n=14,344; 59.2%), followed by the
Netherlands (n=2,835; 11.7%) and the European Union (n=2,164; 8.9%; EU).
Figure 7 presents the geographical distribution by license prevalence,
highlighting the dominance of CC BY licensed articles invoiced to institutions
in the UK, the United States (US), and, to a much lesser extent, the
Netherlands. In contrast, most articles invoiced to institutions from Norway
or representing the EU were published under a non-commercial license.

Figure 7: Centrally Invoiced Elsevier Hybrid OA Articles by Country and CC
License (2015-2019).

Figure 8 shows the yearly distribution of centrally invoiced articles by year
and institutional sector. While UK-based OA invoices were mainly addressed to
discipline-specific governmental and non-profit research funders, invoices to
the Netherlands and Norway were issued to national academic consortia
representing the higher education sector. In 2019, Elsevier also launched
similar agreements in countries with lower publication output including
Hungary and Poland. Besides, we found that invoice recipients from the UK and
the US mainly represented discipline-specific funders, while invoice
recipients from other countries focused on a broad variety of disciplines (see
Table 6).

Figure 8: Centrally Invoiced Elsevier Hybrid OA Articles by Country and Sector
(Per Year). Table 6: Share of Centrally Invoiced Elsevier Hybrid OA Articles
by Country and Subject (2015-2019).

Country/Subject area | Health science | Life sciences | Physical sciences | SSH | Broad | Total
---|---|---|---|---|---|---
United Kingdom | 25% | 11% | 21% | 5% | 0% | 62%
The Netherlands | 0% | 0% | 0% | 0% | 12% | 12%
European Union | 0% | 0% | 0% | 0% | 9% | 9%
United States | 6% | 0% | 0% | 0% | 1% | 7%
Norway | 0% | 0% | 0% | 0% | 3% | 3%
Other | 1% | 0% | 1% | 0% | 5% | 7%
Total | 32% | 11% | 22% | 5% | 30% | 100%

#### Institutional ranking

Table 7 presents the top ten of 63 invoice recipients in our sample. Together,
they accounted for around 80% of centrally invoiced APCs. The table also
highlights the number of distinct journals and the share of CC BY licensed
articles. Notably, UK-based research funders and the US-based Bill and Melinda
Gates Foundation mainly received invoices for CC BY licensed articles. In
contrast, articles invoiced to VSNU, the European Research Council, and Norway
Institutes had a much lower proportion of CC BY.

Table 7: Elsevier Hybrid OA Invoice Recipients (2015-2019).

| Compliance (in %)
---|---
Hybrid OA invoice recipients | Journals | Articles | % | CC BY | OAPC
Engineering and Physical Sciences Research Council | 619 | 4663 | 19 | 97 | 55
VSNU | 357 | 2835 | 12 | 52 | 0
Wellcome Trust | 448 | 2506 | 10 | 98 | 66
European Research Council | 541 | 1986 | 8 | 32 | 9
Medical Research Council | 384 | 1922 | 8 | 95 | 51
Natural Environment Research Council | 203 | 1357 | 6 | 97 | 45
Biotechnology and Biological Sciences Research Council | 309 | 1169 | 5 | 93 | 41
Bill and Melinda Gates Foundation | 254 | 1030 | 4 | 100 | 68
Economic and Social Research Council | 245 | 922 | 4 | 96 | 48
Norway Institutes | 374 | 694 | 3 | 41 | 0
Other | 1012 | 5166 | 21 | 54 | 21
All | 1423 | 24250 | 100 | 76 | 36

The table also highlights the proportion of APCs publicly disclosed through
the Open APC initiative, showing higher disclosure rates for invoice
recipients with a large CC BY share.

##  4 Discussion

From 2015-2019, Elsevier recorded growth in the uptake of hybrid OA: The
number of hybrid OA articles published per year doubled, the number of hybrid
journals with at least one OA article grew by 21%, and the share of hybrid OA
articles relative to closed-accessed articles in these journals increased from
2.6% to 3.7%. As Laakso & Björk (2016), we found only a weak relationship
between the journals’ SNIP and hybrid OA uptake and observed disciplinary
differences. In particular, we found the highest count of hybrid OA articles
in physical sciences journals (see Table 3). This was followed by the life
sciences and health sciences, whereas the social sciences had the lowest
count. This order mostly reflects the disciplines’ overall publication output.
According to the Open Science Monitor (European Commission, 2019), the
physical sciences publish the most articles, followed by the health sciences,
life sciences, and social sciences.

Disciplinary differences in hybrid OA prevalence become more meaningful when
considering the relative share of OA articles to closed-access articles. In
line with previous research, we found that Elsevier journals from the life
sciences and social sciences (Jubb et al., 2017; Kramer & Bosman, 2018; Laakso
& Björk, 2016) recorded greater than typical hybrid OA uptake, whereas
physical sciences journals generally had a lower than typical uptake (Kramer &
Bosman, 2018; Laakso & Björk, 2016; Martín-Martín et al., 2018). In a
systematic review of disciplinary OA publishing patterns, Severin et al.
(2020) highlighted the importance of socio-cultural and technological factors
in shaping publishing cultures and practices. For instance, since many
branches of the physical sciences have established self-archiving practices
(Severin et al. (2020), Björk et al. (2010), Laakso & Björk (2016)),
researchers can provide OA through repositories and might perceive much less
of a need for hybrid OA. In contrast, hybrid OA in the life sciences could be
enabled through project-based funding structures as they allow for easy
integration of publishing costs (Severin et al. (2020). On the other hand, the
high hybrid OA uptake that we observed among the social sciences could point
to the influential role of OA policies and invoicing agreements (Huang et al.,
2020; Larivière & Sugimoto, 2018).

Our invoicing data analysis found that most APCs were invoiced to the author
(n=41,725; 58.2%). However, it is important to emphasize although Elsevier’s
metadata classifies the sponsor type as “author”, this does not necessarily
mean that authors paid for APCs themselves but rather that APCs were not
invoiced through publishing agreements. It is possible that these APCs were
covered through institutional funds or research grants. This would align with
a recent Springer Nature survey that found hybrid OA was predominantly
supported through institutional and funder sources (71%), followed by OA
agreements (34%), while only 6% were paid from personal funds or savings
(Monaghan et al., 2020).

Further, we observed notable differences in licensing. Most hybrid OA articles
invoiced to author were licensed under the more restrictive CC BY-NC-ND
license. Previous research, while lacking dedicated studies on license
selection, suggests that authors tend to select more restrictive license
variants when given a choice (Fraser et al., 2020; Noorden, 2013; Rowley et
al., 2017). On the other hand, we found when hybrid OA was invoiced through
agreements, most articles were licensed under the more liberal CC BY license.
As several funding bodies mandate CC BY licenses, including the UK research
funders that account for 62% of our “agreement” subsample, this result is
perhaps not surprising but suggests the effectiveness of such agreements.

Based on our findings, around a third of the articles were invoiced through OA
agreements (e.g., research funders, national library consortia). The
predominance of UK funding bodies in this subsample reiterates reports from
previous studies that the UK’s OA profile differs markedly from other
countries (cf. Jubb et al. 2015; Jubb et al., 2017), pointing to the impact of
science policy. To promote OA, the UK implemented centralized APC funding and
embraced hybrid OA as a transition model. Within five years of the publication
of the Finch Report in 2012, the UK recorded an 18% increase in immediate OA,
coupled with a rise in hybrid OA from 2.7% in 2012 to 15.4% of all articles in
2016 (Jubb et al., 2017), which can be attributed to the availability of
funding from RCUK. Indeed, RCUK block grants have been the largest single
source of APC funds in the UK—the Wellcome Trust, and more recently
transformative agreements (Jubb et al., 2017; Tickel, 2018). However, since
then publishing expenditures of UK universities have been rising rapidly (Jubb
et al., 2017), so that several universities stopped supporting hybrid OA in
late 2018-2019 (University of Birmingham, n.d.; Walker, 2019). This
development might explain the slight decrease in hybrid articles invoiced to
the UK our data showed around that time (see Figure 7).

Through this study we demonstrated the utility and benefits of publisher-
provided metadata about hybrid OA invoicing and highlighted the need for
extending these to include comprehensive information about licensing and APC
waivers. Metadata guidance should also consider the substantial amount of
delayed OA content, which needs to be distinguished from hybrid OA. Hence, our
study substantiates the recommendations from the Efficiency and Standards for
Article Charges (ESAC) Initiative that seek to increase efficiency and
transparency through improved invoicing and reporting processes and metadata
about OA funding (Geschuhn & Stone, 2017).

While this study advances our knowledge about hybrid OA uptake and invoicing,
the limitations leave room for future research. We focused on only one
publisher, which limits the generalizability of our findings because
Elsevier’s journal portfolio, mix of business models, pricing, and promotion
of various options cannot be assumed to be representative of scholarly journal
publishing in general. Further, although Elsevier’s invoicing data improves
transparency, it seems likely that not all actual OA funding bodies are
disclosed. For instance, most articles were invoiced to authors, but it
remains unclear if the APCs were paid by the authors themselves or through
institutional OA funds or research grants. Research into this topic would
improve our understanding of OA funding outside of publishing agreements.
Moreover, our study demonstrates that comprehensive mapping of the financial
flows of OA publishing requires complex, in-depth country-specific analyses.
Such studies would ideally draw on various data sources to consider research
funders, the consortia landscape, OA policies, and publishing agreements.

This study provides a snapshot of hybrid OA for Elsevier, the largest journal
publisher, prior to the impact of the implementation of Plan S, an initiative
to accelerate the transition to OA that will no longer support hybrid OA
(cOAlition S, n.d.). While many Plan S signatories have already had strong OA
policies, this harmonized approach is likely to affect publishing decisions of
funded authors, the licencing of their articles, and the offerings and pricing
of publishers at a larger scale than before. Because the new requirements
apply to research funded from 2021 onward, a comparative study on articles
invoiced to Plan S signatories would be a fruitful endeavor.

##  5 Conclusion

The primary aim of this empirical study was to investigate Elsevier’s hybrid
OA publishing from 2015-2019 to better understand the volume and invoicing of
hybrid OA and to present a novel, data-driven approach for such analyses. Our
results indicate that although the number of hybrid OA articles has increased
over time, its uptake has remained low. Notably, hybrid APCs were most often
invoiced directly to the authors, followed by agreements, where only a few
funding bodies were the primary drivers of hybrid OA. Finally, our findings
highlight that publisher-provided metadata about the invoicing channels of
(hybrid) OA can facilitate research into and increase the understanding of the
financial flows of OA publishing.

Since the beginning, hybrid OA has been a challenging subject to study due to
the lack of standardized ways publishers flag such content and APC funding
data being limited self-reported data, surveys, and other secondary sources.
This study presented a novel approach to studying APC invoicing that is based
on publicly available publisher-provided metadata, which can be used on on its
own or in combination with other public data sources to gain more detailed and
comprehensive insights into hybrid OA uptake and invoicing. If more publishers
reported OA invoicing on the article level and in a machine-readable format,
this would increase transparency and improve monitoring of the scholarly
journal landscape over time. As hybrid OA has become a central element of OA
policies of research funders and libraries, consumer organizations could
require that invoicing information is added to the article-level metadata. As
long as publishers do not provide this data in a structured and comprehensive
format, they prevent benchmarking prices and therefore hinder competition.

From recent science policy developments in Europe it appears that Big Deals
have gained support and remain firmly in place in the form of transformative
agreements. Through this study we can affirm that hybrid OA is complex as the
financial flows involve research funders, libraries, consortia, and authors.
However, it is on publishers to increase the transparency of OA publishing,
including hybrid OA and transformative agreements, by providing instantaneous
open data about OA uptake and invoicing.

##  6 Data Availability

The source code data analysis is available on GitHub:
https://github.com/njahn82/elsevier_hybrid_invoicing

## References

Bergstrom, T. C., Courant, P. N., McAfee, R. P., & Williams, M. A. (2014).
Evaluating Big Deal journal bundles. _Proceedings of the National Academy of
Sciences_ , _111_(26), 9425–9430. https://doi.org/10.1073/pnas.1403006111

Björk, B.-C. (2012). The hybrid model for open access publication of scholarly
articles: A failed experiment? _Journal of the American Society for
Information Science and Technology_ , _63_(8), 1496–1504.
https://doi.org/10.1002/asi.22709

Björk, B.-C., Welling, P., Laakso, M., Majlender, P., Hedlund, T., & Guðnason,
G. (2010). Open access to the scientific journal literature: Situation 2009.
_PLoS ONE_ , _5_(6), e11273. https://doi.org/10.1371/journal.pone.0011273

Borrego, Á., Anglada, L., & Abadal, E. (2020). Transformative agreements: Do
they pave the way to open access? _Learned Publishing_.
https://doi.org/10.1002/leap.1347

Chamberlain, S. (2020). _crminer: Fetch scholary full text from CrossRef_.
https://CRAN.R-project.org/package=crminer

Chamberlain, S., Zhu, H., Jahn, N., Boettiger, C., & Ram, K. (2020).
_rcrossref: Client for various CrossRef APIs_.
https://CRAN.R-project.org/package=rcrossref

cOAlition S (n.d.). _Plan S: Principles and implementation_.
https://web.archive.org/web/20210129165306/https://www.coalition-s.org/addendum-
to-the-coalition-s-guidance-on-the-implementation-of-plan-s/principles-and-
implementation/.

Crossref. (2020). _March 2020 public data file from crossref_. Crossref.
https://doi.org/10.13003/83b2gp

Elsevier. (n.d.-a). _Agreements_.
https://web.archive.org/web/20210127152729/https://www.elsevier.com/open-
access/agreements.

Elsevier. (n.d.-b). _Open archive_.
http://web.archive.org/web/20210127201740/https://www.elsevier.com/open-
access/open-archive.

Elsevier. (n.d.-c). _Pricing_.
https://web.archive.org/web/20210127152857/https://www.elsevier.com/about/policies/pricing.

Elsevier. (n.d.-d). _Publishing options for: Dutch universities & institutes
associated authors_.
https://web.archive.org/web/20190530214833/https://www.openaccess.nl/sites/www.openaccess.nl/files/documenten/elsevier_-
_vsnu_workflow_updated_18july_v2.pdf.

European Commission. (2019). _Open science monitor: Trends for open access to
publications_. https://ec.europa.eu/info/research-and-
innovation/strategy/goals-research-and-innovation-policy/open-science/open-
science-monitor/trends-open-access-publications_en

Fraser, N., Brierley, L., Dey, G., Polka, J. K., Pálfy, M., Nanni, F., &
Coates, J. A. (2020). _Preprinting the COVID-19 pandemic_. bioRxiv.
https://doi.org/10.1101/2020.05.22.111294

Frazier, K. (2001). The librarians’ dilemma: Contemplating the costs of the
”Big Deal”. _D-Lib Magazine_ , _7_(3).
https://web.archive.org/web/20210125073550/https://librarytechnology.org/document/8950

Geschuhn, K., & Stone, G. (2017). It’s the workflows, stupid! What is required
to make “offsetting” work for the open access transition. _Insights the UKSG
Journal_ , _30_(3), 103–114. https://doi.org/10.1629/uksg.391

Graaf, M. V. D. (2017). _Paying for open access: The author’s perspective_.
Zenodo. https://doi.org/10.5281/ZENODO.438037

Harrison, P. (2019). _What are mirror journals, and can they offer a new world
of open access?_ Elsevier B.V.
https://web.archive.org/web/20210109033031/https://www.elsevier.com/connect/what-
are-mirror-journals-and-can-they-offer-a-new-world-of-open-access

Hendricks, G., Tkaczyk, D., Lin, J., & Feeney, P. (2020). Crossref: The
sustainable source of community-owned scholarly metadata. _Quantitative
Science Studies_ , _1_(1), 414–427. https://doi.org/10.1162/qss_a_00022

Hinchliffe, L. J. (2019). _Transformative agreements: A primer_.
https://web.archive.org/web/20210128170342/https://scholarlykitchen.sspnet.org/2019/04/23/transformative-
agreements/; The Scholarly Kitchen.

Huang, C.-K. (Karl), Neylon, C., Hosking, R., Montgomery, L., Wilson, K. S.,
Ozaygen, A., & Brookes-Kenworthy, C. (2020). Evaluating the impact of open
access policies on research institutions. _eLife_ , _9_.
https://doi.org/10.7554/elife.57067

Jahn, N., & Tullney, M. (2016). A study of institutional spending on open
access publication fees in germany. _PeerJ_ , _4_ , e2323.
https://doi.org/10.7717/peerj.2323

Jubb, M., Goldstein, S., Amin, M., Plume, A., Oeben, S., Aisati, M., Pinfield,
S., Bath, P., Salter, J., Johnson, R., & Fosci, M. (2015). _Monitoring the
transition to open access: A report for the universities uk open access co-
ordination group_.
https://web.archive.org/web/20190523005240/https://www.acu.ac.uk/research-
information-network/monitoring-transition-to-open-access

Jubb, M., Plume, A., Oeben, S., Brammer, L., Johnson, R., Bütün, C., &
Pinfield, S. (2017). _Monitoring the transition to open access: December
2017_. https://www.universitiesuk.ac.uk/policy-and-
analysis/reports/Documents/2017/monitoring-transition-open-access-2017.pdf

Kirkman, N. S. (2018). _A study of open access publishing by NHMRC grant
recipients_ [Curtin University]. http://hdl.handle.net/20.500.11937/77026

Kramer, B., & Bosman, J. (2018). _Towards a Plan S gap analysis: open access
potential across disciplines using Web of Science and DOAJ_ [Data set].
Zenodo. https://doi.org/10.5281/zenodo.1979937

Laakso, M., & Björk, B.-C. (2016). Hybrid open access–a longitudinal study.
_Journal of Informetrics_ , _10_(4), 919–932.
https://doi.org/10.1016/j.joi.2016.08.002

Larivière, V., Haustein, S., & Mongeon, P. (2015). The oligopoly of academic
publishers in the digital era. _PLOS ONE_ , _10_(6), e0127502.
https://doi.org/10.1371/journal.pone.0127502

Larivière, V., & Sugimoto, C. R. (2018). Do authors comply when funders
enforce open access to research? _Nature_ , _562_(7728), 483–486.
https://doi.org/10.1038/d41586-018-07101-w

Lawson, S. (2015). ”Total cost of ownership” of scholarly communication:
Managing subscription and APC payments together. _Learned Publishing_ ,
_28_(1), 9–13. https://doi.org/10.1087/20150103

Lawson, S., Gray, J., & Mauri, M. (2016). Opening the black box of scholarly
communication funding: A public data infrastructure for financial flows in
academic publishing. _Open Library of Humanities_ , _2_(1).
https://doi.org/10.16995/olh.72

Marques, M., & Stone, G. (2020). Transitioning to open access: An evaluation
of the UK Springer Compact Agreement Pilot 2016–2018. _College & Research
Libraries_, 81(6), 913–927. https://doi.org/10.5860/crl.81.6.913

Marques, M., Woutersen-Windhouwer, S., & Tuuliniemi, A. (2019). Monitoring
agreements with open access elements: Why article-level metadata are
important. _Insights the UKSG Journal_ , _32_.
https://doi.org/10.1629/uksg.489

Martín-Martín, A., Costas, R., Leeuwen, T. van, & López-Cózar, E. D. (2018).
Evidence of open access of scientific publications in google scholar: A large-
scale analysis. _Journal of Informetrics_ , _12_(3), 819–841.
https://doi.org/10.1016/j.joi.2018.06.012

Matthias, L. (2020). _Publisher OA portfolios 2.0_ (Version 2.0) [Data set].
Zenodo. https://doi.org/10.5281/zenodo.3841568

Matthias, L., Jahn, N., & Laakso, M. (2019). The two-way street of open access
journal publishing: Flip it and reverse it. _Publications_ , _7_(2), 23.
https://doi.org/10.3390/publications7020023

Mittermaier, B. (2015). Double dipping in hybrid open access – chimera or
reality? _ScienceOpen Research_. https://doi.org/10.14293/s2199-1006.1.sor-
socsci.aowntu.v1

Monaghan, J., Lucraft, M., & Allin, K. (2020). _’APCs in the wild’: Could
increased monitoring and consolidation of funding accelerate the transition to
open access?_ figshare. https://doi.org/10.6084/M9.FIGSHARE.11988123.V4

Nelson, G. M., & Eggett, D. L. (2017). Citations, mandates, and money: Author
motivations to publish in chemistry hybrid open access journals. _Journal of
the Association for Information Science and Technology_ , _68_(10), 2501–2510.
https://doi.org/10.1002/asi.23897

Noorden, R. V. (2013). Researchers opt to limit uses of open-access
publications. _Nature_. https://doi.org/10.1038/nature.2013.12384

OECD. (2015). _Frascati manual 2015: Guidelines for collecting and reporting
data on research and experimental development_. OECD Publishing.
https://doi.org/10.1787/24132764

Pieper, D., & Broschinski, C. (2018). OpenAPC: A contribution to a transparent
and reproducible monitoring of fee-based open access publishing across
institutions and nations. _Insights the UKSG Journal_ , _31_.
https://doi.org/10.1629/uksg.439

Pinfield, S., Salter, J., & Bath, P. A. (2016). The ”total cost of
publication” in a hybrid open-access environment: Institutional approaches to
funding journal article-processing charges in combination with subscriptions.
_Journal of the Association for Information Science and Technology_ , _67_(7),
1751–1766. https://doi.org/10.1002/asi.23446

Piwowar, H., Priem, J., Larivière, V., Alperin, J. P., Matthias, L.,
Norlander, B., Farley, A., West, J., & Haustein, S. (2018). The state of OA: A
large-scale analysis of the prevalence and impact of open access articles.
_PeerJ_ , _6_ , e4375. https://doi.org/10.7717/peerj.4375

Piwowar, H., Priem, J., & Orr, R. (2019). _The future of OA: A large-scale
analysis projecting open access publication and readership_. bioRxiv.
https://doi.org/10.1101/795310

Pölönen, J., Laakso, M., Guns, R., Kulczycki, E., & Sivertsen, G. (2020). Open
access at the national level: A comprehensive analysis of publications by
finnish researchers. _Quantitative Science Studies_ , _1_(4), 1396–1428.
https://doi.org/10.1162/qss_a_00084

Prosser, D. (2015). _The costs of double dipping_.
https://web.archive.org/web/20210128164930/https://www.rluk.ac.uk/the-costs-
of-double-dipping/.

Prosser, D. C. (2003). From here to there: A proposed mechanism for
transforming journals from closed to open access. _Learned Publishing_ ,
_16_(3), 163–166. https://doi.org/10.1087/095315103322110923

R Core Team. (2020). _R: A language and environment for statistical
computing_. R Foundation for Statistical Computing. https://www.R-project.org/

Robinson-Garcia, N., Costas, R., & Leeuwen, T. N. van. (2020). Open access
uptake by universities worldwide. _PeerJ_ , _8_ , e9410.
https://doi.org/10.7717/peerj.9410

Rowley, J., Johnson, F., Sbaffi, L., Frass, W., & Devine, E. (2017).
Academics’ behaviors and attitudes towards open access publishing in scholarly
journals. _Journal of the Association for Information Science and Technology_
, _68_(5), 1201–1211. https://doi.org/10.1002/asi.23710

Schimmer, R., Geschuhn, K., & Vogler, A. (2015). _Disrupting the subscription
journals’ business model for the necessary large-scale transformation to open
access_. Max Planck Digital Library. https://doi.org/10.17617/1.3

Severin, A., Egger, M., Eve, M. P., & Hürlimann, D. (2020). Discipline-
specific open access publishing practices and barriers to change: An evidence-
based review. _F1000Research_ , _7_.
https://doi.org/10.12688/f1000research.17328.2

Shieber, S. M. (2009). Equity for open-access journal publishing. _PLoS
Biology_ , _7_(8), e1000165. https://doi.org/10.1371/journal.pbio.1000165

Tickel, A. (2018). _Open access to research publications – 2018_.
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/774956/Open-
access-to-research-publications-2018.pdf

University of Birmingham. (n.d.). _UKRI open access block grant_.
https://intranet.birmingham.ac.uk/as/libraryservices/library/research/open-
access/funding/ukri-open-access-block-grant.aspx

Unpaywall. (n.d.-a). _What does is_paratext mean in the API?_
https://web.archive.org/web/20201126131640/https://support.unpaywall.org/support/solutions/articles/44001894783.

Unpaywall. (n.d.-b). _What do the types of oa_status (green, gold, hybrid, and
bronze) mean?_
http://web.archive.org/web/20210127192910/https://support.unpaywall.org/support/solutions/articles/44001777288.

Unpaywall. (n.d.-c). _What is an OA license?_
http://web.archive.org/web/20210127192625/https://support.unpaywall.org/support/solutions/articles/44002063718-what-
is-an-oa-license-.

Walker, D. (2019). _Research Councils UK open access funding 2019-2020_.
Library & Archives Service at The London School of Hygiene & Tropical
Medicine. https://blogs.lshtm.ac.uk/library/2019/03/05/research-councils-uk-
open-access-funding-2019-2020/

Wickham, H., Averick, M., Bryan, J., Chang, W., McGowan, L. D., François, R.,
Grolemund, G., Hayes, A., Henry, L., Hester, J., Kuhn, M., Pedersen, T. L.,
Miller, E., Bache, S. M., Müller, K., Ooms, J., Robinson, D., Seidel, D. P.,
Spinu, V., … Yutani, H. (2019). Welcome to the tidyverse. _Journal of Open
Source Software_ , _4_(43), 1686. https://doi.org/10.21105/joss.01686