One role of government is to invest in public infrastructure: roads, bridges, public water and sewage, the military, etc. The FRED graph above shows this investment in fixed assets (by all levels of U.S. government) as a percentage of GDP.
We see several clear phases: 6-7% in the 1950s and 1960s, 5% in the 1970s and 1980s, 4% in the 1990s and 2000s, and around 3.5% since 2010.
As noted above, this includes military investment, which can explain the higher levels that coincide with the height of the Cold War. The subsequent decline, however, can possibly also be explained with military expenses: National defense as a percentage of GDP has declined, as our second graph shows.
This graph includes consumption expenditures for national defense: These expenditures are for services or things that don’t last more than a year, such as fuel, wages, and contractor costs.
It’s also possible that the non-defense components of fixed assets declined. Or not. We can’t come to any conclusions from just these data.
How these graphs were created: Search FRED for “government fixed assets.” From the “Edit Graph” panel, use “Edit Line 1” to add a series for nominal GDP (as the fixed assets series is nominal) and apply the formula a/b*100. For the second graph, repeat the exercise by searching for “defenses expenses.”
Suggested by Christian Zimmermann.