The United States has the lowest personal savings rate of any developed country, and national surveys indicate U.S. teenagers do not understand the complexities of the nation's banking, investing, and credit systems.

How do taxes work? How costly is credit? How do you balance a checkbook? Invest in the stock market? Buy insurance? Plan for retirement? A financially literate adult must be able to answer questions like those.

And, says Dara Duguay, who heads a coalition of government agencies and financial institutions promoting financial literacy, all too many young adults can not.

Take the cost of credit, for example. Many Americans who rack up credit card debt do not realize how much the interest payments cost them in the end.

"If you owe $1,000 on your credit card at 17 percent interest, and you only make the minimum monthly payment, you will be in debt for 12 years, and by the time you finish paying it off, you will have paid an additional $1,000 in added interest," Ms. Duguay says.

There are other ways that financial illiteracy can be costly. Many Americans throw money away daily on lottery tickets, Dara Duguay says, because they do not realize how infinitesimal their chances are of winning.

"You have a greater chance of contracting a flesh eating bacterial disease than winning the lottery. So, if you are waiting for the lottery to solve your financial problems, you are probably going to be waiting for a long time," Ms. Duguay explains.

Jane Schuchardt, who directs financial literacy courses for the Agriculture Department, says another misconception is that the stock market offers an opportunity to "get rich quick."

In truth, she says, the best way to make money in the stock market is to invest carefully and plan to leave your money in for a long time. "There are very few get-rich-quick situations out there, very, very few. The regular consumer makes money by saving consistently, starting to save early, and making really sound decisions along the way," Ms. Schuchardt says.

And by taking care to understand extremely complicated U.S. financial services sector. "Banking has become very complex. Investing has become very complex. Even basic savings has become complex because there are so many choices," she says.

Those complexities make financial literacy more difficult to attain, she says, but they also make it more essential today than ever before.