There is widespread concern, both in the private and public sectors, about perceived declines in U.S. college graduates in STEM fields. In our sample, the proportion of science majors has remained steady over the sample period; however, the number entering our college intending to major in STEM fields has fallen. In this paper we use administrative data from the graduating classes of 2001-2009, roughly 5000 graduates, from a northeastern liberal arts college to model the progression of students through STEM majors. The results suggest that absolute and sometimes relative grades are important, as is the intended major (as reported on the admissions application). AP credits are also strongly correlated to taking a first course, but diminish in the more selected samples. Simulations suggest that if science grade distributions were more like the college average, there would be roughly 2-4% more students progressing in STEM departments. (Contains 6 tables and 2 figures.)