In 1980, the U.S. Bureau of the Census reported a census count of 226,549,448 persons on Census day, April 1st. No one knows the true number of persons living in the U.S. Beginning in 1950, demographic analysis methods were used to estimate the net census undercount, The most recent estimates of net undercount were 1% for 1980 (assuming 2.0 million illegal aliens included in the 1980 Census enumeration); 2.8% for 1970; 3.3% for 1960 and 4.4% for 1950.