It doesn't appear to be common knowledge but there may be an affordable car crisis in the United States. The latest Bankrate.com Car Affordability Study found:     

"…typical households in most of America's larger cities don't earn enough to afford the average new vehicle, under a common budgeting rule for buyers… The '20/4/10' rule says you should aim to put down at least 20 percent of a vehicle's purchase price, take out a car loan for no longer than four years, and devote no more than 10 percent of your annual income to car payments, interest, and insurance. If you can't stay within those lines, you can't afford the car."

The only major city where a new car remains affordable is Washington, D.C.!

For some, the obvious solution is choosing a less expensive model. For others, the answer is buying a used vehicle. For the latter group, here's some bad news: even an average-priced used car – nationally, the average price is about $19,200 – is unaffordable for households in eight of the 25 largest cities.

Leasing is also an option; one that may have helped create an oversupply of used cars. In July, Automotive News reported:

"…millions [of] cars that were leased two or three years ago, many of them used compact and midsized cars with low mileage, are heading toward auction lots and used car dealerships. That surge in supply threatens to depress prices for new and used vehicles, raising the risk of losses for automakers and finance companies on lease deals. It also undercuts the value of cars customers want to trade in for a new vehicle."

The rising popularity of ride-sharing and car-sharing, and the introduction of self-driving vehicles, may also depress prices. In fact, some automakers have introduced their own ride-sharing services.