A high school degree confers not only higher expected lifetime earnings, but also reduced earnings volatility and lower risk of unemployment. College graduates on average have much higher expected lifetime earnings compared to high school graduates, but because they also face higher earnings volatility our results suggest the value of college degree declines with risk aversion. Accounting for progressive income taxation, unemployment insurance, and Social Security taxes and benefits further reduce the value of education. Overall, we conclude that the value of a college (high school) degree to be $300k to $500k ($200k to $250k), depending on the parametric assumption of risk aversion. While the returns to a college education remain high relative to the cost of a college education (both in terms of direct costs as well as foregone earnings while in school), the net gains are substantially below those commonly reported in the popular press.
That is from the new paper "Risk and Returns to Education" by Brown, Fang, & Gomes (November 2012).