<P> Barber says a decline in the population growth rate is likely to affect the demand for housing, and claims this is apparently what happened during the 1920s . He concludes: </P> <P> the rapid and very large decline in the rate of growth of non-farm households was clearly the major reason for the decline that occurred in residential construction in the United States from 1926 on . And this decline, as Bolch and Pilgrim have claimed, may well have been the most important single factor in turning the 1929 downturn into a major depression . </P> <P> The decline in housing construction that can be attributed to demographics has been estimated to range from 28% in 1933 to 38% in 1940 . </P> <P> Among the causes of the decline in the population growth rate during the 1920s were a declining birth rate after 1910 and reduced immigration . The decline in immigration was largely the result of legislation in the 1920s placing greater restrictions on immigration . In 1921, Congress passed the Emergency Quota Act, followed by the Immigration Act of 1924 . </P>

When was the great depression and what caused it