We would like to believe that our career success is all because of brains and hard work, but economic research tells us that a fair amount of it comes down to accidents of birth and timing. Finishing college at the wrong time, for example, can be costly.

“Graduating in a typical sized recession leads to about a 10 percent earnings decline,” says UCLA economist Till von Wachter. “And that 10 percent decline lasts about 10-15 years.”

But don’t make the mistake of doubting the value of a college degree.

“The negative impact of a recession is generally lower among college grads than among people who do not have that college education,” explains Neeta Fogg, with Drexel University’s Center for Labor Markets and Policy.

So those graduating in coming years shouldn’t get smug if they outperform their older siblings: they might not be smarter than them — they definitely had better timing.