Half the houses in the USA in 1940 didn't have indoor plumbing. They didn't ask in previous censuses, probably because it wasn't a relevant question which means

Half the houses in the USA in 1940 didn't have indoor plumbing. They didn't ask in previous censuses, probably because it wasn't a relevant question which means 50% in 1940 was a climbing number and everything below that was less than 50. "Plumbing Facilities In 1990, only 1 percent of our homes lacked complete plumbing facilities. But, things were much different in 1940, when nearly half lacked complete plumbing. Then, about ten States had rates approaching or exceeding 70 percent. In succeeding decades, the proportion of homes lacking complete plumbing dropped dramatically, falling to about one-third in 1950 and one- sixth in 1960. It is interesting to note the States with the lowest percent- age of such homes in 1940 were higher than Alaska, which topped the 1990 list."