Private colleges with the biggest payoff

20-year return on investment: $867,000
Annualized return: 13%
Total 4-year cost of attendance : $229,100

This Rhode Island-based university encourages students to create their own courses of study across a wide variety of disciplines.

The school's open curriculum seems to be paying off. Students earn an average salary of about $55,000 in the first five years after school, according to PayScale.

While less than a fourth of Brown's graduates earn science, technology, engineering or math degrees, biology and economics are among the school's most popular areas of study, according to the U.S. News and World Report.

Brown is one of the oldest schools in the country, and like other highly-selective Ivy League schools, it attracts academically-driven students with high earning potential, said PayScale's Frank.

"The more selective schools are letting in fewer students and picking from the cream of the crop," she said. "Were those students going to be successful regardless of where they attended?"

First published March 10, 2015: 1:18 PM ET

Source: PayScale
Based on employee survey data, PayScale calculated total median pay for each private school's undergraduate alumni over a 20-year period and compared it to the median pay for a high school graduate over 24 years. The return on investment (ROI) in 2014 dollars was determined by taking the difference between those median pay figures and subtracting the cost of attending the school in 2014 -- including tuition, room and board, and other costs -- and adjusting for scholarships and grants. The annualized ROI is calculated by dividing the earnings differential by the total cost and represents the percent of expected ROI received each year after graduation. Unlike in previous PayScale reports, the earnings differentials in this report do not take into account graduation rates. Alumni who attended graduate school or other higher education were excluded.

8 of 10