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If you want to get ahead financially, it pays to choose your parents carefully.

Simply put, affluent parents are able to provide many of the underpinnings of a middle-class (or better) life for their offspring. Wealthier parents may offer cash for a down payment so their kids can become homeowners, or they may cover health insurance premiums to protect their children from catastrophic medical bills.

Most importantly, though, wealthier parents can help pay for one of the most important factors in economic success: a college degree. Increasingly, that single factor is giving their kids a crucial advantage that seems to be slipping from the grasp of children from lower-income families.

Consider some of the research on economic mobility in the United States:

People born at either end of the economic spectrum are likely to stay there

Research shows that if your folks were rich, you'll likely be rich too, or at least well off. If your folks were poor, you likely will struggle financially as well.

Forty percent of those raised in the top 20% of incomes in the U.S. remain in that high-income bracket as adults, according to research by the Pew Charitable Trusts, and 63% remain above the middle. Similarly, 40% of those raised in the bottom 20% of incomes stay there as adults, and 70% remain below the middle. There's still some economic mobility, of course, but there's less than you'd find in Canada, Western Europe and even traditionally class-bound Great Britain, according to research by Scandinavian economist Markus Jantti.

The Pew study also found that a four-year college degree is an important determinant of economic success. Researchers found that college degrees help prevent "downward mobility," keeping those born in higher-income brackets from falling out, while allowing those in lower-income brackets to move up.

Gap between rich and poor in college attendance, completion is growing

Liz Weston

Liz Weston

Two University of Michigan researchers studied college attendance patterns of people born between 1961 and 1964 and compared them with those born between 1979 and 1982.

Over the course of one generation, college attendance and completion rates soared among those in the higher income brackets. In the lower brackets, the rate of increase was much less dramatic, widening the gap between rich and poor.

For example, 80% of those in the highest income bracket attended college in the early 2000s, compared with 58% of the same income group 20 years earlier. The highest income bracket included people with incomes in the top quartile.

Only 29% of those in the lowest quartile of income attended college in the 2000s, up just 10 percentage points from the 19% rate seen in the early 1980s.

Even more telling is the rate of college completion. Among young people who came from the highest-income households, 54% completed college, up from 36% two decades ago. Among the lowest-income group, the college completion rate went from 5% to 9%.

Parents torn between providing access and teaching responsibility

Some of my readers say they want their kids to pay for all or some of their own college educations -- to teach them responsibility. Others cite the importance of setting aside money to improve the odds their children will complete school.

For example, Chris Hubbard of Thousand Oaks, Calif., doesn't want his kids to disappear into the work world before they get degrees. Hubbard said his parents and grandparents paid for his and his sister's college education, so they could graduate without student loans.

"I will do my best to do the same for my kids. I want them to be able to go directly to college after high school without first working for a year" or more, Hubbard wrote on my Facebook page. "Once they get used to having some money, it is tough to give up a full-time income and lessen their living standard for improved future income."

Matt Furrier of Boston agrees. He put himself through school, commuting to a state college, an experience he doesn't want his children to repeat.

"(M)y wfe & I absolutely will pay for the bulk of their private colleges! I want much better for them," Furrier wrote on my Facebook page. "We can afford to do it."

Working your way through school often doesn't work

Chris and Matt may have a point. Those who "go it alone" financially are far more likely to drop out of college. Nearly 6 out of 10 college dropouts reported that they had to pay for school themselves, according to research by Public Agenda for the Bill & Melinda Gates Foundation. Of those who completed college, more than 6 in 10 said they had help from parents or other relatives.

The main reason for dropping out wasn't the cost of college, the researchers said. Those who failed to complete school were almost twice as likely to cite problems juggling work and school as their main reason as they were to blame tuition bills.

Students who drop out after trying to use loans to bridge the gap in parental support often end up with the worst of all possible worlds: big debts with no degree to help them dig their way out. Even those who succeed in borrowing their way to a degree can find themselves with intolerably high levels of debt.

Elizabeth Knox of Costa Mesa, Calif., wrote that she wants something better for her daughter.

"Graduating with no debt and student loans has given me opportunities my peers do not have. Buying houses, disposable income, and a different lifestyle," Knox wrote. "I will provide my daughter the same opportunity."

The bottom line

If you weren't prescient enough to pick rich parents or you're a parent who can't help much with college costs, what do you do?

First, don't fall for the nonsense that post-secondary education is somehow less valuable than it used to be. It's true that college graduates have suffered in the current tough economy, but those without college degrees have suffered more, with bigger drops in income and much higher unemployment rates.

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Focus instead on getting an education you can afford. Community colleges are a great way to get inexpensive vocational training or a start on a four-year degree. Steer clear of for-profit schools, which have a bad reputation for charging a lot and delivering little.

Most of all, persevere. You have to actually get the degree to get the economic benefit. You can get ahead -- but only if you cross that goal line.

Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.

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