Private colleges with the biggest payoff

20-year return on investment: $1,104,500
Annualized return: 12.6%
Total 4-year cost of attendance : $237,700

This small California liberal arts college takes the top spot on Payscale's list of colleges with the best return on investment for the fourth year in a row.

Offering just nine majors focused on science, technology, engineering and math (STEM), the Los Angeles-area school also requires students to take a core curriculum of humanities and social sciences courses.

"Our alumni know how to write, communicate with broad audiences, work across disciplines and work collaboratively rather than competitively," said Thyra Briggs, the school's vice president for admission and financial aid. "We hear repeatedly from employers and graduate schools that our alumni are often 'translators' in their offices and graduate programs."

As a result, grads from this school are often rewarded with high-paying jobs that bring in an average of $1.1 million more over 20 years than a high school graduate, after subtracting the cost of attendance, according to Payscale.

STEM schools usually dominate the PayScale list, and Mudd's holistic approach puts the school at the top, said Lydia Frank, editorial and marketing director at PayScale.

"They're engineers who can communicate," she said.

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.

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