Estimates on the number of ExPats in the United States illegally range from 10 million to 25 million. Why so many? Why don't they just come in legally? Well, the short answer is "if they could, they would." There are huge incentives to draw people to America. It's a rich country with lots of opportunities to earn far more than can be earned in many other countries. Health care is good. Education is good. On the other hand, in order to assure that population growth doesn't outpace infrastruture and economic capacity, the legal channels for entering America are restrictive. And the country has extremely long and porous land borders. Result: many bypass the legal channels.
Let's start with the Mexican day laborer who wants a better life for his family. The legal channel is to apply for a visa. But his purpose in entering the country is to work, and that requires sponsorship from a potential employer. One man, one job. And the job has to be one that can't be filled by someone already in the U.S. legally. In other words, there is almost no chance that a Mexican day laborer will be granted a visa to work in the U.S. It ain't gonna happen. And he won't be given a visitor's visa either, because the law allows the consul to judge his intent and not just the merits of his application. His options are to remain in the cycle of poverty in Mexico, hoping for a cultural shift to end centuries of endemic corruption that stifles the Mexican economy, or to enter America illegally.
Now let's look at a Philipino who has a brother in the United States. That American brother has a growing landscaping business, and he wants his brother to immigrate--with the wife and kids--and become his partner. How hard can that be? Answer: almost impossible to do legally. See the book excerpt at the Filipino Recipes site to get an idea of how strained and complicated it is.
