Baby boomers, who have been reshaping the economy for their entire lives, are doing it again, but in a less macro way. They are depressing prices in the collector car market because they're losing interest in classic American cars from the 1950s -- the cars of their youth.

The bear market in American classics stands in sharp contrast to the demand for historic exotic and foreign cars, which has strongly rebounded from its post-recession slowdown. Last August, a 1967 Ferrari was auctioned for $27.5 million -- a record for a road car. A few months earlier, a 1954 Mercedes race car went for $29.6 million.

Not so for '50s cars from the old Big Three as well as now-defunct makers like Studebaker and Packard. The evidence comes in the March issue of Car & Driver, in an article by Rob Sass of Hagerty Insurance, which specializes in insurance for antique and vintage autos. According to Hagerty's index of prices of '50s American classics, Sass writes, activity peaked in August 2007 and hasn't recovered. The decline affects everything from popular favorites like the Chevy Bel Air to rarities like the Packard Caribbean convertible.

In their prime, baby boomers were big buyers. But now, Sass writes, "their interest in the hobby is starting to wane." Nor does he see the market rebounding any time soon. The millennial generation doesn't have a comparable level of interest. "It's questionable whether they will care about the cars of their grandfathers and great-grandfathers -- or any cars," he adds.

Here are some data points from the post-war era of tailfins, two-tone paint jobs, and whitewall tires. The condition of the cars ranges on a scale from condition four (daily driver with visible flaws) up to condition one (perfectly clean, groomed down to the tire treads). In a few exceptional categories buyers have made money by catching the peak of the market, but the overall trend is down.

The best advice for someone considering a classic car as an investment is to buy what you love; any appreciation should be secondary to the pride of ownership -- and the satisfaction of preserving a slice of history for future generations.