With the level of immigration into the US increasing with time and in various forms and through various channels, it has become imperative for the Americans to make the national security measures all the more strict and strong. In this regard, the Office of Immigration Statistics (OIS), located within the Policy Directorate of the Department of Homeland Security (DHS) maintains immigration statistics to monitor and assess the effects of immigration on the country's security.
Some of the important statistical information on immigration to the US are:
1) Migration: Immigration and Emigration to the US by decade: 1901-90:
The above table (compared years are 1986, 1996, and 2004 as latest available) shows the pattern of immigration to the US by various foreign nationals. While Mexico dominates the immigrant communities (despite various attempts being made by the American authorities by means of anti-immigration laws), India and China have a raised position in the latest figures of 2004 in terms of immigration, which clearly shows that these two countries are front-runners at the moment as far as immigration to the US is concerned. Other observations include: Iranians' reduced immigration after the 1980s after the US-Iran relation deteriorated, and Russians' increased immigration in the mid-1990s following the formal termination of the Cold War.
3) Foreign born as a percentage of the total population, 1990 and 1994 to 2005
This table shows the percentage of foreign-born population in the US. The figure clearly illustrates that the percentage of people of foreign origin in the US is clearly increasing (the comparable years are 1990 and 1994-2005).