Dartmouth's Tuck School of Business has topped a list of the best 50 U.S. business schools for the second time but a survey by Forbes magazine found one-year courses could be a better investment.

Forbes said in a statement that its rankings were based on the return on investment over five years made by alumni graduating in 2002. This took into account earnings since 2002 minus tuition and salary lost during school.

Graduates from a two-year MBA course at Dartmouth's Tuck School of Business had a median five-year gain of $115,000 compared to Stanford alumni reporting a gain of $102,000 and Harvard alumni $94,000.

Students from Dartmouth on average were earning $60,000 a year before attending the MBA program compared to earning an average $180,000 in 2006.

But the fifth biennial ranking found the survey of two-year courses in the United States highlighted the appeal of one-year programs offered overseas.

Each of the top five one-year foreign programs beat out all two-year programs because the opportunity cost, in lost wages, to attend is materially less, said the researchers in a statement.

IMD in Switzerland, which ranked first among such one-year schools, had a median five-year gain of $169,000.

This was followed by Insead in France and Singapore with a median five-year gain of $145,000 and Cambridge in Britain with $139,000.

Forbes, which will publish the results of its survey in its September 3 edition, said it sent surveys to 18,500 alumni of 102 MBA programs worldwide for the survey and heard back from 22 percent of them.

Here is a list of the top 10 U.S. business schools:

1. Dartmouth (Tuck)

2. Stanford

3. Harvard

4. Virginia (Darden)

5. Pennsylvania (Wharton)

6. Columbia

7. Chicago

8. Yale

9. Northwestern (Kellogg)

10. Cornell (Johnson)

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