If you’ve ever gotten slapped with a late fee of $39, or seen your interest rate surge to 29% after making one late payment, you can at least take comfort in knowing you're not a sucker. In fact, the entire credit card industry is oriented to make sure those who revolve their balances each month trip up occasionally, and that they pay dearly for the privilege.

There’s no other way to explain how the credit card industry is able to generate so much revenue from fees and interest. In 2005 alone, credit card companies fleeced $7.8 billion from customers in penalty fees. They raked in another $5.2 billion from cash advance fees. The big kahuna was the $71 billion they made from interest charges.

Clearly, you’re not alone in having your hard-earned dollars eaten away by the credit card monster. The reality is that the credit card industry is set up in a way that some customers pay through the nose, while others enjoy low rates or even free loans each month. In fact, the market is structured so that the folks who need the product the most—those who revolve their balances each month—pay the most.

So who pays the most for using their credit cards? A study commissioned by Demos found that four groups—low-income individuals, African Americans, Latinos and single females—bear the brunt of the cost of credit card deregulation through excessive fees and high interest rates. About one out of three cardholders pay more than 20 percent in interest on their cards. If you have credit card debt and your income is like most 20-somethings—that is, between $25,000 and $50,000—you are nearly two times as likely as households earning more than $50,000, and four times more likely than households earning over $100,000, to pay such high rates. African Americans and Latinos with credit card debt are twice as likely as whites to pay high interest rates.

The ability to charge some customers ridiculously high rates while others pay next to nothing explains an important paradox in the industry; there is competition in the market for new customers, but close to no difference among all the major issuers once you carry a balance. For example, card companies sent out 8 billion solicitations in 2006 trying to drum up new customers. You may have even gotten one or a dozen of the tantalizing offers promising a low or even 0% interest rate, along with a rewards program offering points that add up to free stuff. But know this, as soon as you start carrying a balance from month to month—it doesn’t really matter what card you’ve got in your wallet. All the major card issuers feature similar terms: high penalty interest rates and fees, the ability to retroactively apply rate increases, and the right to change terms at any time, for any reason.

I’m not saying the credit card issuers shouldn’t make money off those of us who for whatever reason find ourselves in debt. But those profits should be generated from decent business practices, not through deception and gotcha tactics. Can it be done? Sure. Let’s use one of the nation’s biggest lenders as an example. In 2006, Citigroup reported after-tax profits from mortgages, student loans, and car loans of 0.79 percent. But their after-tax profits for the same year on credit card lending were much, much bigger: a whopping 6.17 percent. Why? Because compared to other types of lending, the credit card business is much less regulated—it’s the Wild West of the lending business.

I’ve said it before, and I’ll say it again here, it’s time for some common sense rules to be injected into this marketplace. And it’s up to Congress to do so. If you haven’t already, contact your U.S. Senator and Representative and let them know you’re tired of the endless fees, unpredictable interest rate changes, and gobblygook disclosures.