Approximately one out of every five persons 1 year old and over in continental United States changed his place of residence between April 1956 and April 1957, according to the results of a sample survey conducted by the Bureau of the Census, Department of Commerce. In April 1957, 31.8 million persons, or 19.4 percent of the population, were living in a different house from the one in which they had been living in April 1956. As in other years, the majority were living in a different house but in the same county (intracounty movers). Of the remaining 10 million mobile persons, the number who had moved between States )interstate migrants) was about equal to the number who had moved between counties within the same State (interstate migrants).