<p>Math (and possibly physics) may be slightly different. I know that at MIT for instance, many science and engineering undergrads are involved in sponsored research with key professors who often run large labs on campus. Most of these professors are actually quite eager to retain the undergrads they worked with for continued graduate work. They know them well, the students are already trained and are generally very strong students. That built-in advantage is hard to overcome. Each department is completely autonomous in its admission decisions and a strong recommendation by a tenured professor is often all that is needed. MIT grad school is actually by far the single largest destination of MIT undergrads. Not all go for PhDs, but many do. </p>
<p>It would be interesting to get Mollie’s breakdown of the baccalaureate origins of the students in the Harvard biology department.</p>