The diplomatic history of the United States oscillated among three positions: isolation from diplomatic entanglements of other  nations ; alliances with European and other military partners; and unilateralism, or operating on its own sovereign policy decisions. The US always was large in terms of area, but its population was small, only 4 million in 1790.  Population growth was rapid, reaching 7.2 million in 1810, 32 million in 1860, 76 million in 1900, 132 million in 1940, and 316 million in 2013.  Economic growth in terms of overall GDP was even faster. However, the nation's military strength was quite limited  in peacetime before 1940.
Question: How many years did it take for the US population to grow from 132 million to 316 million?
Answer: 73