### Database Schema:
CREATE TABLE PaperAuthor (
	PaperId	INTEGER	NULL,
	AuthorId	INTEGER	NULL,
	Name	TEXT	NULL,
	Affiliation	TEXT	NULL,
	foreign key (AuthorId) references Author (Id),
	foreign key (PaperId) references Paper (Id)
);

CREATE TABLE Author (
	Id	INTEGER	NULL	PRIMARY KEY,
	Name	TEXT	NULL,
	Affiliation	TEXT	NULL
);

CREATE TABLE Paper (
	Id	INTEGER	NULL	PRIMARY KEY,
	Title	TEXT	NULL,
	Year	INTEGER	NULL,
	ConferenceId	INTEGER	NULL,
	JournalId	INTEGER	NULL,
	Keyword	TEXT	NULL,
	foreign key (JournalId) references Journal (Id),
	foreign key (ConferenceId) references Conference (Id)
);

CREATE TABLE Journal (
	Id	INTEGER	NULL	PRIMARY KEY,
	ShortName	TEXT	NULL,
	FullName	TEXT	NULL,
	HomePage	TEXT	NULL
);

CREATE TABLE Conference (
	Id	INTEGER	NULL	PRIMARY KEY,
	ShortName	TEXT	NULL,
	FullName	TEXT	NULL,
	HomePage	TEXT	NULL
);

### User's Query:
What is the average number of papers published in the journal "Molecular Brain" every year from 2008 to 2011?

### Extra Knowledge:
"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