To calculate ROI for a specific degree, we first determined the overall cost of the degree. We allowed the degree holder four years to graduate. Using data from a recent College Board study, we assigned a figure of $37,343 as an average cost of a four-year public liberal arts degree, and a figure of $121,930 for degrees earned at four-year private colleges. The total cost included tuition, room and board, and books, and did not factor in scholarships or grants. We then determined the median cash compensation over the course of 30 years of typical jobs requiring that degree using Salary.com data. We used current Salary.com figures, but added 4.3% per year to account for inflation and cost of living increases. To determine ROI, we subtracted the cost of the degree from the gains over 30 years, then divided that figure by cost.