To be fair, it's easy to make a mistake during a census. Especially when you have a family as big as Liston's. Even so, at 34 years old that's fairly old for a fighter. Men like Frazier, Marciano, Dempsey, were all retired at that age. Men like, Ali, Louis, Tyson were shells of themselves at that age. Sure their were people just as good as they'd ever been (Holyfield, Lewis) but they were the exception, not the norm. That's not even taking into account Liston's inactivity having fought 6 minutes and 14 seconds in 3 years, coming in overweight, and with a (recorded) injury.
There are a lot of mistakes in the U.S. Census, but Sonny was not listed in the 1930 U.S. Census Records. Curtis, Sonny's brother, was born in late 1929 and is listed in the 1930 census. But Curtis and Sonny (as Charles), both at ten years of age, are listed in the 1940 U.S. Census. However, if Sonny was not a twin of Curtis, it is likely that he was born in the latter part of 1930 at the very earliest. This is assuming that Curtis and Sonny had the same mother. - Chuck Johnston