SELECT T3.name FROM exhibition_record AS T1 JOIN exhibition AS T2 ON T1.exhibition_id  =  T2.exhibition_id JOIN artist AS T3 ON T3.artist_id  =  T2.artist_id GROUP BY T3.artist_id HAVING avg(T1.attendance)  >  200
Show all artist names with an average exhibition attendance over 200.
[Schema (values) (types)]: | theme_gallery |  artist : artist_id (text) , name (number) , country (text) , year_join (text) , age (number) | exhibition : exhibition_id (text) , year (number) , theme (text) , artist_id (text) , ticket_price (number) | exhibition_record : exhibition_id (text) , date (number) , attendance (text);