This might help for creating an initial analysis: https://www.ycombinator.com/companies/founders

Of 11,162 YC founders who haven't opted out of the directory, the top 9 alma maters account for nearly exactly 20% of founders.

    540 - Stanford University
    388 - University of California, Berkeley
    373 - Massachusetts Institute of Technology
    193 - University of Waterloo
    187 - Harvard University
    144 - Carnegie Mellon University
    143 - Columbia University
    143 - University of Pennsylvania
    124 - Cornell University

I don't know what you'd compare this to for "society at large" but of the 500 CEO's in the Fortune 500, the top 9 alma maters account for about 16% of those CEO's.

    25 - Harvard University
    11 - Stanford University
    9 - University of Pennsylvania
    7 - Massachusetts Institute of Technology
    6 - Cornell University
    6 - University of Chicago
    6 - Northwestern
    6 - Columbia University
    6 - Yale