it should be more than 50. Asso is the foundation of a consulting firm (the major source of project leaders, partners). Those firms will keep or slightly squeeze the asso pool even in bad time. Roughly estimate, MBB will recruit around 40 ppl. So if you add MONITOR, BAH and others, the number will be bigger.
Let's do a simple back-of-envelope test. Say there will be 15 students each top 15 us school+5 euro school, then u get the number of 300. 100 of them will stay in US or euro. 50 will pursue a tough life in finance. Another 50 will stay with the industry they previously worked in. then only 100 ppl will compete for the consulting positions in mainland. It seems most of them can be satisfied.
Mck in 2008 recruited 15-20 associates, i don't know the number in 2009, but given the market turned better, the number should be at least around 15. i don't if BCG and BAIN offered another 20 openings.