Private colleges with the biggest payoff

private college roi california institute of technology

20-year return on investment: $1,029,700
Annualized return: 13.4%
Total 4-year cost of attendance : $221,600

Caltech is a science and engineering powerhouse and students who graduate from this school go on to innovate and change the world.

They also see a great return on their college education.

Students who graduate from this Pasadena, California university earn an average of about $1 million more over 20 years than those who graduate from high school, according to Payscale's data.

This research university is the home of NASA's Jet Propulsion Laboratory, which produces robotic space explorers like the Mars Rover, as well as the Caltech Seismological Lab, which monitors and studies earthquakes in the area. The school is also known for producing patents and Nobel prizes.

Over 80% of Caltech's graduates stay in California, where the state's wealth of high-paying jobs helps to boost the school's return on investment, said PayScale's Frank.

"Caltech has a 3-to-1 student-faculty ratio, immersing students in groundbreaking research," said Alexx Tobeck, executive director of the Caltech Alumni Association. "Our students made an impact in the world while they were here and they continue to make a profound difference in their career and communities once they have graduated."

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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