Directly comparing postgraduate earnings of workers with bachelor’s degrees and those with only a high school diploma overstates the earnings gains of the college graduates. This bias, called selection bias, stems from the self-selection of high school graduates into college. This study explores the earnings premiums of postsecondary awards and degrees in Washington state, but corrects for this selection bias using a statistical method called propensity score matching. This method compares the earnings of those who received postsecondary awards and degrees with high school graduates who received no degree, but who were comparable in many other measurable ways.
Among other things, we discovered: