Immigration has been a controversial subject periodically in this country throughout much of the past 150 years and has reappeared prominently on the political agenda. Much of the current controversy focuses on illegal immigration, which is at an all-time high. The U.S. Census Bureau estimates their number at 10–11 million. Between 2000 and 2004, there was a net increase of 4.3 million immigrants, close to half of whom are illegal. In broader terms, the controversial political discussions have revolved around competition for jobs, cost of schooling, housing, crime, and so on. A total of 34 million immigrants, both legal and illegal, are now in the United States, the largest number in the history of the country. Some of the legal migrants – about 700,000 a year currently – fill important professional specialties but also bring along immediate family and relatives (about two-thirds of the arrivals).

However one evaluates the net costs and benefits of immigration, it is a major demographic force as well as a political issue in the United States. In Europe, the issue has been pushed to the front of the political agenda as a result of the sustained low level of fertility that is now resulting in actual or imminent population declines along with increasingly aging populations that carry serious implications for retirement pensions and labor force shortages.