Used cars from the Cash-for-Clunkers program sit in the Ted Britt Ford dealership storage lot in Fairfax, Virginia
The average age of U.S. vehicles reached a record in 2011, but that number should decline or flatten as auto sales increase in the coming years. Reuters

Automobile retailer CarMax (NYSE:KMX) plunged 9.36 percent, as of 10:38 a.m. EDT, despite reporting better-than-expected earnings this morning.

Third quarter earnings were $82.4 million, or 36 cents per share, up from 33 cents from the same period last year and beating the consensus analysts' estimate of 34 cents per share.

Revenues rose 23 percent to $2.12 billion and beat expectations of $1.97 billion.

Despite this impressive performance, CarMax may have disappointed the heightened expectation of investors, who have bid up its shares by over 9 percent from December 1 to December 20.

Tuesday's drop takes prices below November 30's closing level.

Nyse