<p>It should be pointed out that according to Caltech's commencement data, of the people who graduated with PhD's from Caltech in the last few years, the undergrad program that they most commonly came from was Caltech itself.</p>
<p>For example, in 2005, of those earning PhD's from Caltech, 7 of them did their undergrad at Caltech. Only 4 came from MIT, 6 from Harvard, 3 from Stanford, 6 from Berkeley (a 7th did his MS at Berkeley), 5 from Princeton, 5 from UIUC, 4 from Michigan, 3 from Cornell, 2 from Chicago, 1 each from Yale, CMU, and UCLA. </p>
<p><a href="http://pr.caltech.edu/commencement/05/phd.pdf%5B/url%5D">http://pr.caltech.edu/commencement/05/phd.pdf</a></p>
<p>In 2004, 8 such people came from Caltech undergrad. 3 from MIT, 6 from Harvard (a 7th completed an MA at Harvard), 5 from Princeton, 5 from Berkeley (a 6th completed MS at Berkeley), 4 from Cornell, 3 from Illinois, 3 from Chicago, 2 from Michigan, 1 from CMU, and 0 from Stanford and Yale (although one person did get an MS from Stanford). </p>
<p><a href="http://pr.caltech.edu/commencement/04/phd.pdf%5B/url%5D">http://pr.caltech.edu/commencement/04/phd.pdf</a></p>
<p>Now one might say that perhaps this is a case of geographic yield. For example, those who go to Caltech for undergrad may get used to the milieu and therefore prefer to stay there for grad-school (just like Harvard people may prefer to stay at Harvard, Stanford people may prefer to stay at Stanford, etc.). On the other hand, Caltech has a tiny undergraduate population compared to those other schools. MIT, for example, has about 4 times the undergrads that Caltech does. Yet the numbers indicate that there are far more Caltech undergrads than MIT undergrads who eventually get PhD's at Caltech. Hence, the geographic yield issue and the size issue probably cancel each other out. </p>
<p>The bottom line is that a strikingly large number of Caltech undergrads stick around for grad school. Whether you think going to Caltech for undergrad really does reduce your chances of getting into Caltech grad school or whether it's bad for your professional prospects to stay is a matter of opinion. But I think there can be no dispute that plenty of undergrads stay for grad school.</p>