Question: What is the average number of papers published in the journal "Molecular Brain" every year from 2008 to 2011?
SQL: 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