To create a comparison group, we dr

To create a comparison group, we drew a random sample of 13,564 doctorate degree holders from the UMI Proquest Dissertation database, which contains the vast majority of doctoral degree recipients from U.S. universities. The random sample was constructed to mirror the distribution of academic disciplines (e.g., microbiology, biochemistry, etc.) and degree grant years in the group of commercial scientists identified in SEC filings. Thus, the sample is stratified by scientific discipline and Ph.D. year to correspond to the distributions of these attributes in the group of academic entrepreneurs. The members of the random sample were then tracked forward from the time they obtained their degrees.