Preliminary May data suggests that month may have seen a minor dip in retail sales volume per dealership. NADA is projecting that reporting dealers sold an average of 6.1 used trucks in May. That number would be off April’s average by 0.5 trucks, but ahead of last May by 0.7.

As the graph illustrates below, May was a comparatively slow month in both 2010 and 2011.

Seasonality may be one reason for this behavior – the traditional explanation is that truckers get their acquisitions out of the way early in the year so they can concentrate on hauling as Spring arrives. That rationale is typically used to explain new truck purchasing trends, but could apply to the used truck market as well. However, we are not generally strong believers in this explanation, since external factors such as EPA-driven pre-buys and economic conditions have overshadowed seasonal factors for most of the past decade.

We suspect that the continued tight supply of trucks with under half a million miles is a more likely cause. With prices historically high even as the average mileage of available sleeper tractor hits 550,000 miles, buyers may be making the jump to new trucks. This may be one reason why new truck sales have increased every month this year.

Pricing is of course the other piece of this puzzle. We will look at preliminary May pricing before the end of this month. Stay tuned.