Immigration into the United States fluctuated throughout the 20th century because of varying economic conditions. But the changes made by the Immigration Reform and Control Act of 1986 drastically increased the number of immigrants allowed into the United States. The chart below depicts the increase in population per decade during the 20th century with a brief description below of how immigration numbers affected the's goal of reducing annual legal and illegal immigration to more traditional numerical levels enjoys broad based public support. Virtually every major poll that has been conducted in the past decade finds that a majority of Americans support lower immigration numbers.