I sympathise with your predicament as I remember when I was about to take the plunge that I was hesitant without knowing about any statistics. Unfortunately, since there is no body overseeing pilot careers from when they graduate it would be very hard to compile such information.
The most reliable sourse is going to be from each of the schools which you visit. Many of the larger ones will have such information available pertaining to their own success. However it should, of course, be taken with a pinch of salt. The stats may be "How many graduates now have jobs as pilots." That, would include the ones that spent two years in McDonalds and then paid for an instructor rating out of desperation and now work part time as an instructor on the days that they're not in McD.
Good luck in your search.