Since the 1990s, the U.S. Census has occasionally asked people about their military experience, including whether they had served in Vietnam. There were some interesting results. In 1995, the census data showed 11.2 million people said they served during the Vietnam war period. But only nine million American actually served in the armed forces during the official Vietnam war period (1964-1975, most U.S. troops were out of Vietnam by 1972, and the big build up didn't begin until 1965). And only 30 percent of those were actually in Vietnam. That's 2.7 million troops. The census estimated that, by 1995, only...