Average Age Of US Motor Vehicles

From Federal Reserve Bank of St. Louis, Economic Research, "The Cyclicality of the Aging U.S. Motor Vehicle Fleet" by Bill Dupor:

American car owners have been replacing their vehicles less frequently, causing the U.S. motor vehicle fleet to age (Figure 1).
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Source: Federal Reserve Bank of St. Louis

Source: Federal Reserve Bank of St. Louis

Figure 2 plots an index of the number of vehicles in use (green line) and an index of per capita new-vehicle sales (blue line). [Each variable in Figure 2 is measured in per capita terms.]