Illegal immigration into the United States, Western Europe, Japan, and other rich countries grew rapidly from about 1990 to the beginning of the financial crisis, and has sharply declined since then. The largest number of illegal immigrants enter the United States, especially from Mexico, but the number of Mexicans crossing the border illegally has apparently slowed to a trickle during the past several years. Some observers have attributed much of the decline from Mexico to tightened border security, stricter search laws against illegal immigrants enacted by Arizona and some other border-states, and greater enforcement against employers who use illegal immigrants. These are part of the explanation, but the main factors are economic and demographic, and some of these are likely to be permanent.
The great majority of immigrants all over the world, both legal and illegal, move for economic reasons: to find jobs that pay a lot more than they can earn in their origin countries. For example, the average illegal immigrant in the United States from Mexico appears to earn about three to four times what he would earn in Mexico. This is why virtually all the illegal (and legal) immigration is from poorer to richer countries. Immigration increases when poorer countries are hit by recessions and financial crises, and by internal conflicts that make life there dangerous and more uncertain.
Illegal immigration is especially sensitive to recessions and other causes of weak job markets in richer destination countries. Illegal immigrants are usually the first to be laid off partly because they tend to be unskilled, and unskilled employees are let go in much larger numbers than are skilled employees. In addition, illegal immigrants tend to have low seniority since they are young, and employees with lower seniority are generally fired first when bad times hit.
Laid off illegal immigrants usually do not qualify for unemployment compensation, and other safety net benefits. This is why many illegal immigrants return home after losing their jobs, even though that means they must bear the costs and risks of possible future illegal entry. It also explains why the flow of illegal immigrants to the United States has slowed to a trickle, given the sharp and sustained rise in American unemployment, especially among younger and unskilled workers.
High unemployment in the United States is presumably only temporary, although it has already persisted for several years. Other more permanent factors have also been reducing the flow of illegal immigrants from Mexico. One important long-term force is the sharp decline in birth rates in Mexico during the past 30 years. The total fertility rate- that is, the number of children born to the average women over her lifetime- has declined in Mexico from almost 7 children in 1970 to over 3 children in 1990, and to only about 2 children at present. This means that Mexican fertility is now not any higher than American fertility, even though Mexico is much poorer.
The very high fertility rates in Mexico in the 1970s and 1980s produced many young Mexicans in the 2000s. This is an important determinant of why illegal immigration from Mexico peaked during 2000-2006 since most illegal immigrants are young. They can more easily bear the hardships and risks of crossing illegally into the United States, and they can look forward to higher earnings for a longer time. Moreover, high Mexican fertility rates in say 1980 produced many Mexican workers in their twenties after the year 2000, which put downward pressure on their earnings and job prospects.
Outmigration from poorer countries like Mexico, especially of illegal immigrants, tends to fall rather sharply when job availability and incomes in their countries are improving at a good pace. This has been happening in Mexico for the past 15 years. The growth in real per capita Mexican incomes since 2000 has raised Mexico’s per capita income by about 40%. Job markets have become a little more open as well, and average years of schooling have increased significantly, so that better paying jobs are much more readily available in Mexico.
Most immigrants, especially illegal immigrants, prefer not to leave if economic prospects are reasonably good in their own countries, even if their earnings would be considerably higher in richer countries. Individuals and young families prefer to stay with their parents, siblings, and friends, and with a culture they grew up with rather than becoming strangers in countries with different cultures. This is especially true for persons who would have to migrate illegally from Mexico since they bear the physical and other risks of crossing the Mexican-US border, have difficulty returning to see their families and friends, and they can be sent back at if apprehended.
Low birth rates and hopefully also growing incomes are likely to be part of the Mexican landscape for a long time. These forces should greatly reduce the long-run flow of illegal immigrants to the US after the American economy recovers from the financial crisis, and even without stepped up apprehension of illegal immigrants. Mexicans who would like to immigrate to US could better afford to wait for visas and other permits to cross the border legally since they now have decent economic prospects while in Mexico.
I argued before on these pages that immigration, especially legal immigration, is good for a country like the US that has many opportunities for ambitious and hard-working men and women. The US should respond to the economic progress and fertility declines in Mexico, elsewhere in Latin America, and also in Asia by expanding greatly the number of legal immigrants accepted (see my monograph The Challenge of Immigration, 2011 for a proposal to sell openly the right to immigrate). Expansion of legal immigration would be good for America, and it would also further cut down the number of illegal immigrants by enabling more of them to come legally and gain the many advantages of legal status.