Approval applications were filed for 55 percent of the drugs that made it to Phase III testing, and 80 percent of those gained eventual approval, although only about half were approved on their initial FDA review.

The 80 percent approval rate, while seemingly high, is down from 93 percent seen in studies of earlier years.

Its a 2011 article: http://www.reuters.com/article/2011/02/14/us-pharmaceuticals-success-idUSTRE71D2U920110214