This data series stretches back to January 1976. Since that first data point, the Civilian Noninstitutional Population Age 16 and Over (i.e., driving age, not in the military, or an inmate) has risen about 66%.
Here is a chart, courtesy of the FRED repository, of the raw data for the seasonally adjusted annualized number of new vehicles sold domestically in the reported month. This is a quite noisy series, to be sure. The absolute average month-over-month change is 4.4%.
The latest data point is the May count published by Motor Intelligence, which shows a seasonally adjusted annual rate of 16.9 million units, which is a 1.0% decrease from the previous month’s figure from the BEA.
The first chart shows the series since 2007, which illustrates the dramatic impact of the Great Recession. The blue line smooths the volatility with a nine-month exponential moving average suggested by our friend Bob Bronson of Bronson Capital Markets Research. The moving average reduces the distortion of seasonal sales events (e.g., Memorial Day and Labor Day weekend) and thus helps us visualize the trend.