Go figure: The stocks of publicly traded dealership groups have posted some pretty hefty gains during the past month.

In fact, the stock prices of nine dealership groups shot up an average of 40% from Nov. 25 to Dec. 19. The increases come despite the fact that some of these companies have shed dealerships and posted quarterly losses and lower vehicle sales volume.

To be honest, I’m not really sure how to explain the gains. The stocks of America’s Car-Mart [ticker: CRMT] and Asbury Automotive [ticker: ABG] have climbed 39% and 35%, respectively, in the past month. Lithia Motors’ stock [ticker: LAD] shot up 86%, and Sonic Automotive’s [ticker: SAH] skyrocketed 131%.

The stock of CarMax Inc. [ticker: KMX] was down 6% for the month. Before posting a $21.9 million loss on Friday, though, its stock had been 6% higher.

I suppose some of these dealership groups are benefiting from buyers looking for used vehicles rather than new ones, but I can’t imagine that’s the sole reason. If you’ve got any thoughts about it, feel free to comment here.