How countries select among types of immigrants is one way to address the question, why do countries accept immigrants at all? Based on actual migration patterns, the reason is primarily to add to the workforce, secondarily for other purposes.
There are four countries conceived as immigrant-based: Australia, Canada, New Zealand and the United States. In 2006, the first three accepted on average as permanent residents the equivalent of 1% of their population. Work-based immigration, awards based primarily on worker skills, was one third of one percent of the population. Assuming a workforce of 50% of the total population, that comes to 0.67% of the workforce.
The United States admitted the equivalent of 0.4% of its population. Work-based legal immigration (based on skills) was equivalent to 0.06% of the workforce – one tenth the rate of the other three. Assuming that illegal immigration, averaging 2000 – 2015, was 300,000 a year, and that 75% of illegals worked, the illegal workforce addition was three times the number of permanent awards for legal workers.
This disparity between the United States and others is the greater share of permanent award to families. The U.S awards 70% of permanent status to family member. Many of these family awardees do work, but they are not awarded on the basis of skill. Assuming that half of these immigrants work, that comes to a total of 75,000 legal work-based, and 400,000 new legal workers and 225,000 illegal workers, for a total workforce gain of 700,000.
Proposals to shift to a more skill-based system, combined with better enforcement of immigration laws, would make some 800,000-plus skilled based, perhaps half of them skilled workers, the other seasonal or low skilled.
Germany in 2006, with 27% of the American population, made twice our number of skill-based awards.
2006 immigration data from Pia Orrenius and Madeline Zavodny, Beside the Golden Door: U.S. Immigration Reform in a New Era of Globalization, 2010), pg. 57