How many miles do Americans drive each month, each year, over the past 10 years…? FRED has the answers. The red line on the graph is a monthly series of miles driven. As you can see, it varies greatly according to the seasons of the year, which should surprise no one. One can clearly see the upward trend, but all the jaggedness makes it more difficult to see what’s been happening for the past 10 years or so. Has there been a recent decline?

To investigate, we can use a 12-month moving average of sorts that can be created in FRED. (This graph appears below the first one.) While some moving averages include about 6 months before and 6 months after a point in time, this moving average takes the average of the 12 preceding months, which smooths the series to make it more readable. In addition, this average is divided by the civilian noninstitutional population—that is, likely drivers. (The same result would be achieved if those below age 16 were removed from the overall data.) This second depiction makes it much clearer that, per capita, Americans are driving less these days.

How this graph was created: Search for “Vehicle Miles Traveled,” then add the data series “Moving 12-Month Total Vehicle Miles Traveled.” Add yet another series, “Civilian Noninstitutional Population,” but this time select the option to modify existing data series 2. For series 2, select right y-axis position and create the data transformation “a/b.”

Suggested by Christian Zimmermann