Y! Big Story: Six things to know about U.S. immigration

The U.S. Supreme Court's hearing on Arizona's SB1070 comes at a time when illegal immigration from Mexico has fallen. The argument over unauthorized entry has drowned out some intriguing developments in America's overall migrant population, including a rebound in international students in higher education and legal citizenship. Below, some facts and figures about who's coming, going, and staying:

The United States has the world's largest immigrant population. No surprise, with its history of having open-door policies and welcoming newcomers with open arms. You would have to combine the migrant populations of Russia, Germany, Saudi Arabia, and Canada—which rank second through fifth in terms of their migrant populations—to equal the migrant population of the United States.

Other numbers, according to the Migration Policy Institute:

  • About 40 million foreign-born residents live in the United States.

  • Immigrants make up 13% of the U.S. population. The record all-time low was 5% in 1970; the all-time high 15% in 1890.

  • Currently, one in eight U.S. residents—and one in six U.S. workers—is foreign-born.

  • The U.S. isn't one of the top 10 countries with the highest share of immigrant population. That honor belongs to Qatar; 87% of its residents have come from abroad.

  • An estimated 11.5 million migrants are unauthorized.

  • Nearly half of all illegal migrants live in California (25%), Texas (16%), and Florida (6%).

The slowdown of migration from the south. Pew's report on the net immigration flow from Mexico has received the most buzz. It confirms what demographers have said for some time: After 40 years and 12 million migrants, the influx of Mexicans to the United States has slowed.

The standstill appears to be the result of many factors, including the weakened U.S. job and housing construction markets, heightened border enforcement, a rise in deportations, the growing dangers associated with illegal border crossings, the long-term decline in Mexico's birth rates and changing economic conditions in Mexico. (April 23, Pew Hispanic Center)

[Related: Net Migration from Mexico Dips to Zero]

Mexico still fuels the immigrant population. About 30% of foreign-born residents hail from Mexico. China accounts for 5%, followed by India and the Philippines.

Looking back over the entire span of U.S. history, no country has ever sent as many immigrants to this country as Mexico has in the past four decades. However, when measured not in absolute numbers but as a share of the immigrant population at the time, immigration waves from Germany and Ireland in the late 19th century equaled or exceeded the modern wave from Mexico. (April 23, Pew Hispanic Center)

The so-called brain drain, exaggerated? Recent reports have taken a look at more privileged migrants who are returning to their parents' birthplace.

In growing numbers, experts say, highly educated children of immigrants to the United States are uprooting themselves and moving to their ancestral countries. They are embracing homelands that their parents once spurned but that are now economic powers. (April 15, New York Times)

An article from the Wharton School of the University of Pennsylvania also reports on Indian migrants who don't want to wait out the busted U.S. economy.

[Alok] Aggarwal [cofounder and chairman of research and analytics firm Evalueserve] adds that the current wave of reverse migration is fuelled more by the constraints in the developed economies rather than the opportunities in India. "The uncertain job scenario and the long wait for the Green Card in the U.S., for instance, are making people question the relevance of staying there. And the India growth story makes it easier for them to return." (Dec. 13, 2011, Knowledge@WhartonToday)

A study from the Migration Policy Institute found that migrants who left the U.S. did so to take advantage of their homelands' incentives. MPI Director of Communications Michelle Mittelstadt, in an e-mail to Yahoo!, points to the "relatively large movements of Eastern European and Brazilian migrants back to their homelands and vibrant economies and the difficulty of countries with lagging economies such as Spain and Japan to get immigrants interested in the pay-to-go programs they were offering."

So far, though, the evidence is anecdotal. Wealthier migrants have always been more fluid in terms of where they settle, and doesn't reflect the overall numbers.

America is still alluring. Take a look at the higher-education system: For generations, many who earned their degrees in the U.S. stayed here after graduation. There was an attendance dip for several years after the September 11 attacks, as U.S. borders were restricted. But people seeking higher education here have returned in full force. In fact, 2011 was a record year for international student enrollment, with 32% more international enrollees than a decade ago. Of the $21 billion added to the U.S. economy through educational expenses, the greatest amount came from China.

Another confirmation of the United States as a go-to destination: Legal immigration is back up after a dip in 2010. "Of course, many of those people have been in the pipeline waiting for years for a green card, so there is pent-up demand," Mittelstadt says. "A more flexible indicator would be nonimmigrant admissions, which did decline after the onset of the recession, but have rebounded."

Migration helps baby boomers.

This population surge gains in importance as baby boomers age and as younger generations step up into the workforce. Compare that with Japan, known for its strict citizenship policies: The Japanese population saw a record plunge in 2011, right as its boomer population is facing retirement. Or, look at China, which has a massive population but "will be older than the United States within a generation." America's replenished numbers should mean its position as a world leader should stand strong in the coming years.