Not a single year Chinese account for >15%. Big year around 15% (15-18), small year around 6% (6-8). Every year there is 1-3 (10-20%) from top regulatory background (SAFE, CSRC, stock exchange...), most these guys indeed have little interest of switching to IB/MC.
In 2009 and 2010, it is possible for the 80%. If you check H/S/W, possibly the figure is also below 90% for the two years. And, the fact that some students do not get full time offer is not that they could not get one. It's imply that they are not giving up hope for career switch to IB/PE etc, and would not consider going back to pre-MBA, even with 50-200% salary increase.
Again, if you do not know, you had better shut up.