See the FAA statistics pages. Here's the one for 2012 (2013 is not out)-

US Civil Airmen Statistics

I've looked at various statistics such as the number of ATPs by year, see my chart, and it does not support the notion of a large pilot shortage in the airlines. To criticize my chart however, I should add something about total number of jobs by year to show the disparity between pilots and jobs, as well as the number of "active" pilots who are not actually present in the US work force and perhaps cross ref it with the number who hold first class medicals.