Source: U.S. Census Bureau

The easiest way to get your foot in the door is for your dad to hold it open for you.

That's because even though the Good Ole Boy Network might not be what it used to, it still very much exists. At least that's what a new paper by Martha Stinson and Christopher Wignall of the U.S. Census Bureau shows us. They looked at Census and tax data for 35,454 working-age sons in 2010 to see how many of them were at the same companies as their dads. The answer was 9.6 percent, although, as you can see above, it was even higher for the sons of the top 10 percent. For a bit of perspective, that's somewhere between 10 and 20 times more than we'd expect by random chance.

Remember, though, this was just a snapshot from a single year. If we broaden the picture out, we see that, before their thirtieth birthday, 22 percent of sons have worked with their fathers. And it wouldn't be surprising, based on other countries, if this was much higher for the highest-income families. Indeed, economist Miles Corak has shown that 70 percent of the sons of Canada's top 1 percent have worked someplace their dads did.

But nepotism ends once kids are in the door — though that's more than enough. See, sons who work with their fathers tend to make more than ones who don't, but not more than other entry-level workers in the same field.

So their paychecks are bigger because their dad's gotten them a better job than they could otherwise find, not a better salary for that job. But the money's just a bonus. It's really about the experience. It's getting a leg up in the never-ending arms race for the perfect, or at least good enough, resumé.

That's why rich kids, who have the least need but the most to gain, work with their dads more often than anyone else. And it's part of the reason why poor college grads have a harder time getting ahead than their better-off peers (and sometimes even rich dropouts). They just don't have the same built-in networks or financial support systems to land a more lucrative, though less certain, job, let alone take a chance on one.

Inequality, like success, has many fathers, none more than your own.