In the auto industry, "upside-down" has nothing to do with gymnastics or playtime. It's the term used for folks who owe more on their car than it's worth. Typically, a lot more.

What's also known as "negative equity" is a big and growing problem. Almost 29 percent of car "owners" are currently upside-down. Edmunds.com estimates that the average person in such a circumstance is almost $3,800 behind. That is, he or she owes that much more on a car than the amount for which it could be sold.

Rather than discouraging shoppers who are already in that troubled state from signing up for a new model - or at least for a sharp secondhand car - most dealers are happy to take them on as customers. When the paperwork is finalized, that hapless motorist finds himself or herself deeper yet into a morass of debt. We can safely bet, too, that there will be yet another visit to the dealership - long before today's new car is paid for.

Simple math demonstrates why this keeps happening. The moment you drive a new or late-model car off the sales lot, it loses a hefty chunk of the value it had moments earlier. The new car has suddenly become used. The late-model used car, for which the buyer has paid a retail-level price, is now worth only a wholesale amount - what another dealer would be willng to pay for it, for resale to someone else. Since the difference between retail and wholesale value is sizable, the only way to overcome this disparity is to start with a large down payment. Picking a car that depreciates slowly rather than rapidly doesn't hurt, either.

Let's take an example: a secondhand 2005 Elegance sedan that costs $15,000 at the dealership. Wholesale, that car might be worth $12,000. If you turn over a $3,000 down payment (including your trade-in, if any), you're at least breaking even to start. If your trade and down payment total only $2,000, you're $1,000 in the hole right off the bat. And since the difference between wholesale and retail can be considerably more than $3,000, many buyers wind up in seriously dire straits.

But that's just the beginning. In addition to seeking low down payments, most of today's shoppers want their monthly payments as low as possible. There's only one way to make it so: stretch the payments out over a longer term. The average loan period for a new car is now over 69 months, according to CNW Marketing Research, with an average monthly payment of $402. Used-car buyers face an average loan period of just over 41 months, paying almost $217 per month on average.

During each of those extra months, the car loses even more of its value - yet you're still paying for it. For credit-challenged customers, too, the interest rate will be a lot higher, which means the total amount paid is considerably greater than the car was ever worth.

Sadly, most consumers - and those in the auto business - don't seem terribly worried. An occasional news story surfaces about upside-down car owners, but for the most part, negative equity is accepted as normal. A massive and highly profitable "cottage industry" has grown up, catering specifically to credit-troubled shoppers.

How can you avoid getting into this sort of financial woe? Two solutions stand out:
1. Don't buy a car unless you can offer a sizable down payment, and avoid excessively long-term loans.
2. If you do find yourself upside-down, drive that car until it drops. Negative equity is only an issue if you sell or trade-in that car at some point in its early life. So, don't let yourself be tempted by another new car unless the first one becomes troublesome.

Avoiding temptation is too much for most of us, unfortunately. From childhood on, we're taught that we should be able to buy just about anything we want, without fretting too much about how to pay for it. As teenagers, we start eagerly down the path to overwhelming debt loads. And if we're not careful in controlling purchases, automotive and otherwise, going upside-down becomes a permanent state.

In Arthur Miller's prize-winning play, Death of a Salesman, Willie Loman finally reaches the day when his mortage is paid off, and he and wife Linda are "free and clear." Nowadays, few of us even seem to see "free and clear" as a fantasy, much less a goal to be achieved at some point.

As Mad Magazine's Alfred E. Neuman would put it: "What, me worry?"