You may be surprised to learn that the Ivies only account for 6% as this Techcrunch article illuminates:

We found that the 628 U.S.-born tech founders we surveyed received their education from 287 unique universities. Almost every major U.S. university was represented. The top ten institutions in this group accounted for only 19 percent of the entire sample. In other words, 81% of the tech company founders came from “regular” schools. To make my colleagues at Harvard feel better (and to keep my job), I’ll acknowledge that the Ivies represented 8% of the sample even though those schools only graduate 1.6% of American students.

Then we broadened our research and looked into the backgrounds of the founders of 549 successful businesses across a set of high-growth industries. The proportion of Ivy-Leaguers was even smaller (about 6% of the sample). We also found that MBA’s tended to start companies sooner after graduation (13 years) than bachelors degree holders (17 years). And both these groups were quicker to the startups than PhD’s – who typically waited 21 years from the time they graduated to start their ventures. That’s right, tech company founders aren’t spring chickens. Also, we found that Computer Science/IT grads were faster than MBA’s (13 years vs. 15 yrs) and the applied science majors (20 years).

A fascinating tidbit at the end of the article:

Company founders also value their education. In a paper which the Kauffman Foundation will release on Nov 17 (during Global Entrepreneurship Week), we report that 70.3% said their university education was important. Ivy League graduates valued their education even more, with 85.7% indicating this was important. Surprisingly only 18.8% believed that university or alumni networks were important. Of the Ivy graduates, 28.6% ranked these networks as important.