1. A computer-implemented method comprising: collecting sample test information from a plurality of test-only structures of a first wafer, prior to completion of said first wafer; gathering finished test data from all die of said first wafer, after completion of said first wafer; constructing a yield prediction model based on said sample test information and on said finished test data; and predicting, using said model, a percentage of die of said first wafer that will meet a particular specification.