Even in today’s very tough job market, a college degree is the best long-term investment – by far, promising higher returns than stocks, bonds, housing, and even gold, according to a study released this week by the Brookings Institution.

The Washington, DC-based think tank crunches some interesting numbers:

On average, a four-year degree is the equivalent of an investment that returns 15.2% a year. That’s more than double the average return to stock market investments since the 1950s, which average 6.8%; more than five times the return to investments in corporate bonds, which return 2.9%; gold at 2.3%, long-term government bonds at 2.2% and housing at 0.4%.

Admittedly, a college education demands pretty hefty costs upfront.

Researchers Michael Greenstone and Adam Looney estimate costs of a four-year college degree at $102,000 and about $28,000 for a two-year associate’s degree. This factors in the typical costs of tuition and fees (minus room and board, since as researcher noted, you eat and sleep whether or not you go to college), as well as pay that students give up if they had spent their years right after high school working instead of going to college.

Pretty steep. But long-term, the costs are well worth it, the study found. At 22, the average college graduate earns about 70% more than the average person with a high school degree only. In other words, the study notes, at the peak of their earning power, the average worker with only a high school diploma earns only about as much as a college graduate one year out of school.

And it only gets better from there. In 2010, a college graduate at age 50 (career peak) earns about $46,000 more than someone with only a high school diploma.

So a college degree is almost always the best long-term investment. Indeed, U.S. unemployment continues to hover at an annoyingly high 9% or so. And the job market has been especially tough for younger workers.

Then again, as Fortune’s Anne Fisher pointed earlier this week, things might be looking up. The number of freshly minted grads with bachelor’s degrees finding jobs this year surged 22% to 35,372, or 8% more than in 2009, according to CollegeGrad.com.

So for those feeling a little hopeless about the prospects out there, now is as good a time as any to start job hunting.

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