Now that the consortia have joined together (Bham and Warks) it is going to be rather tricky to work out what the increase in applicants really means. In previous years, many will have applied for both exams, although some would have applied for only Warks or only Bham.
What is clear though is that the birth rate did increase across the city and West Midlands. The biggest jump (baby boom) was in 2006/7 according to the Bham statistics I have seen. That includes many children in the year group starting Year 4 soon (and my own dc4
The birth rate and net migration into Birmingham has continued to grow but not by as great a jump seen in 2006/7 (which if anyone can remember, were good years economically).