National Origins Formula is an umbrella term for a series of qualitative immigration quotas in America used from 1921 to 1965, which restricted immigration from the Eastern Hemisphere on the basis of national origin. These restrictions included legislation and federal acts. Since there is no one formula that can account for each law or restriction across the decades, as the scale, variables, and demographic characteristics change per law, the concept of National Origins Formula is best described as a collection of quantitative data considerations in immigration and migration laws in the United States. History Temporary measures establishing quota limits per country based on the makeup of the foreign-born population residing in the U.S. were introduced in 1921 (Emergency Quota Act) and 1924 (Immigration Act of 1924); these were replaced by a permanent quota system based on each nationality's share of the total U.S. population as of 1920, which took effect on July 1, 1929 and governed American immigration law until December 1, 1965 (when the Immigration and Nationality Act of 1965 abolished it). The National Origins Formula aimed to preserve the existing ethnic proportions of the population as calculated according to data from the 1920 Census of Population. The 1921 Emergency Quota Act restricted immigration to 3% of foreign-born persons of each nationality that resided in the United States in 1910. The Immigration Act of 1924, also called the National Origins Act, provided that for three years the formula would change from 3% to 2% and the basis for the calculation would be the census of 1890 instead of that of 1910. After June 30, 1927, total immigration from all countries will be limited to 150,000, with allocations by country based upon national origins of inhabitants according to the census of 1920. The quota system applied only to non-Asian immigrants. It aimed to reduce the overall number of unskilled immigrants, to allow families to re-unite, and to prevent immigration from changing the ethnic distribution of the population. The 1924 Act also included the Asian Exclusion Act, which limited immigration to persons eligible for naturalization. As a result, East Asians and South Asians were effectively banned from immigrating. Africans were also subjected to severe restrictions. Immigration from North and South America was not restricted. National origins computation Under the Immigration Act of 1924, the Bureau of the Census and Department of Commerce were tasked with estimating the National Origins of the