What is the average number of papers published in the journal "Molecular Brain" every year from 2008 to 2011?
"Molecular Brain" is the FullName of journal; year from 2008 to 2011 refers to Year BETWEEN 2008 AND 2011; average = Divide (Count(Id),4)
SELECT CAST(COUNT(T2.Id) AS REAL) / COUNT(DISTINCT T2.Year) FROM Journal AS T1 INNER JOIN Paper AS T2 ON T1.Id = T2.JournalId WHERE T1.FullName = 'Molecular Brain' AND T2.Year BETWEEN 2008 AND 2011
database name:db_id authors
Author table Author Cols: Id dtype integer, Name dtype text, Affiliation dtype text, 
Conference table Conference Cols: Id dtype integer, ShortName dtype text, FullName dtype text, HomePage dtype text, 
Journal table Journal Cols: Id dtype integer, ShortName dtype text, FullName dtype text, HomePage dtype text, 
Paper table Paper Cols: Id dtype integer, Title dtype text, Year dtype integer, ConferenceId dtype integer, JournalId dtype integer, Keyword dtype text, 
PaperAuthor table PaperAuthor Cols: PaperId dtype integer, AuthorId dtype integer, Name dtype text, Affiliation dtype text, 
