Immigration to the United States is not totally determined by shifts in flow that occur as a result of lawmakers revising the allocations.
Immigration to the United States plummeted in the middle of the 20th century largely as a result of factors brought on by the Great
Depression and World War II.
There are a variety of “push-pull” factors that drive immigration.
Push factors from the immigrantsending countries include such circumstances as civil wars and political unrest, economic deprivation and limited job opportunities, and catastrophic natural disasters.
Pull factors in the United States include such features as strong employment conditions, reunion with family, and quality of life considerations.
A corollary factor is the extent that aliens may be able to migrate to other “desirable” countries that offer circumstances and opportunities comparable to the United States.
Department of Homeland Security, Office of Immigration Statistics, multiple fiscal years. Aliens legalizing through the Immigration Reform and Control Act of 1986 are depicted by year of arrival rather than year of adjustment.
The annual number of LPRs admitted or adjusted in the United States rose gradually after World War II, as Figure 1 illustrates.
The DHS Office of Immigration Statistics (OIS) data present those admitted as LPRs or those adjusting to LPR status.
The growth in immigration after 1980 is partly attributable to the total number of admissions under the basic system, consisting of immigrants entering through a preference system as well as immediate relatives of U.S. citizens, that was augmented considerably by legalized aliens.19
The Immigration Act of 1990 increased the ceiling on employment-based preference immigration, with the provision that unused employment visas 19 The Immigration Reform and Control Act of 1986 legalized 2.7 million aliens residing in the United States without authorization.
In addition, the number of refugees admitted increased from 718,000 in the period 1966-1980 to 1.6 million during the period 1981-1995, after the enactment of the Refugee Act of 1980.
Many LPRs are adjusting status from within the United States rather than receiving visas issued abroad by Consular Affairs before they arrive in the United States.
In the past decade, the number of LPRs arriving from abroad has remained somewhat steady, hovering between a high of 481,948 in FY2012 and a low of 358,411 in FY2003.
Adjustments to LPR status in the United States have fluctuated over the same period, from a low of 244,793 in FY1999 to a high of 819,248 in FY2006.
As Figure 2 shows, most of the variation in total number of aliens granted LPR status over the past decade is due to the number of adjustments processed in the United States rather than visas issued abroad.
In any given period of United States history, a handful of countries have dominated the flow of immigrants, but the dominant countries have varied over time. Figure 3 presents trends in the top immigrant-sending countries (together comprising at least 50% of the immigrants admitted) for selected decades.
The figure illustrates that immigration at the close of the 20th century was not as dominated by 3 or 4 countries as it was earlier in the century.
These data suggest that the percountry ceilings established in 1965 had some effect.
As Figure 3 illustrates, immigrants from only three or four countries made up more than half of all LPRs prior to 1960.
By the last two decades of the 20th century, immigrants from seven to nine countries comprised about half of all LPRs and this pattern has continued into the 21st century. http://www.simonebertollini.com/Immigration-Law/Business-Immigration/H-1B-Visa-Entrepreneurs.aspx
Although Europe was home to the countries sending the most immigrants during the early 20th century (e.g., Germany, Italy, Austria-Hungary, and the United Kingdom), Mexico has been a top sending country for most of the 20th century and into the 21st century. Other top sending countries from FY2001 through FY2010 are the Dominican Republic, El Salvador, Colombia and Cuba (Western Hemisphere) and the Philippines, India, China, South Korea and Vietnam (Asia).