Labor markets are heavily distorted by immigration restrictions, producing wide and persistent wage differences for observably identical workers in developed and developing nations. Income for low skilled American workers is 16 times as high as Haitians in Haiti, about 7 times as high as Indians in India, and about 4 times as high as Mexicans in Mexico—all adjusted for purchasing power parity. Just by moving here immigrants can largely close that wage gap.
There are very limited avenues for low skilled immigrants to immigrate legally, which raises an important question: if the economic benefits of immigrating are so high, why are there only 11 to 12 million unlawful immigrants here?
Below are the two broad reasons:
First, the benefits of immigrating are not as high as they seem. The probability of being employed in the destination country is a vital variable because unemployment does not confer any benefits on the immigrant. The skill level of prospective unlawful immigrants restricts job opportunities to certain occupations. If the sectors where low skilled immigrants work have high unemployment rates, as many do now, the chances of earning higher wages here is lower so the economic benefits of immigration are lower. Downward wage bargaining by immigrants is limited but unlawful immigrants do take a wage cut, all else being equal, of about 20 percent to compensate their employers for the legal risk of hiring them and other reasons. Growing economies in places like Mexico, China, and elsewhere might partially offset the benefits of immigrating by promising higher incomes in the near future.
Second, the cost of unlawfully immigrating is very high. Opportunity costs, search costs (including language barriers), transportation costs, legal costs, the probability of dying en route, the probability of being sold into slavery, and the probability of not making it to the United States despite paying the smuggling fee are all high and increase risk. Immigration enforcement is very effective at deterring most would-be unlawful immigrants. High smuggling fees are a high up front cost.
Immigration can be understood as an investment over a period of years. The length of time the immigrant spends here employed at higher wages increases the economic benefits of immigrating. The costs of immigrating, like paying for a smuggler, are fixed while there seems to be a low marginal cost for staying here to avoid immigration enforcement. The psychic costs could shift with time.
Here is an example: