US Infrastructure Spending Has Been A Fairly Constant Share Of GDP For 30 Years

From CBO, "Public Spending on Transportation and Water Infrastructure, 1956 to 2014," Report, March 2, 2015:

Source: CBO

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Public Spending on Transportation and Water Infrastructure Has Been a Fairly Constant Share of Economic Activity for 30 Years
As a share of GDP, public spending on transportation and water infrastructure over the past three decades has hovered at about 2.4 percent, which is 0.6 percentage points lower than the peak of 3.0 percent in 1959. That share rose briefly in 2009 and 2010, to 2.7 percent, as a result of the temporary increase in federal outlays brought about by the enacting of the American Recovery and Reinvestment Act of 2009 (ARRA). [Emphasis added.]