The American Community Survey, conducted by the U.S. Census Bureau, publishes detailed estimates on the veteran population each year. ACS data typically only counts veterans no longer in active service—in other words, people who are currently civilians.
Veterans make up a significant but declining percentage of the U.S. population, as veterans of older wars pass on. In 2011, there were nearly 1.9 million living veterans of World War II. By 2016, that number had dwindled to less than 700,000.