<p>MIT gives a pretty substantial advantage in its graduate admissions process to MIT undergrads. About half of MIT grads who choose to grad school go to a graduate program at MIT (raw numbers [url=<a href="http://web.mit.edu/career/www/infostats/graduation05.pdf%5Dhere%5B/url">http://web.mit.edu/career/www/infostats/graduation05.pdf]here[/url</a>], on page 5 of the pdf). Unfortunately, I don't know of any statistics from the other end, but here's what I do know.</p>
<p>I know that EECS explicitly reserves 20% of its graduate program seats for MIT graduates, and that doesn't count the 50% of each EECS class which enters the MEng program, which is reserved specifically for MIT undergrads. So about 60% of MIT EECS undergrads go on to get a graduate degree of some kind from MIT (125 MEng students, ~20 SM/PhD students).</p>
<p>In my fiance's department, aero/astro, the department's policy is "accept all the MIT grads and give them good financial packages so they won't go to Stanford." :)</p>