By Jason Richwine

The problem of illegal immigration is no longer confined to a handful of states and municipalities. Though California still hosts about one-quarter of the nation’s estimated 10.8 million illegal immigrants, many illegals are settling in non-traditional places. Georgia now hosts more than Arizona, with North Carolina not far behind. Even Minnesota has over 100,000 illegal immigrants.

If the Reid-Schumer-Menendez immigration-reform bill currently being floated in Congress passes, nearly all of America’s illegal immigrants could become legal immigrants in the coming years. The legal, ethical, and political ramifications of such a policy will be the subject of robust public debate in the near future. This debate should start with the facts about illegal immigrants themselves: How many are here (and how do we count them)? Where do they come from? How long have they been here? What skills do they bring with them? Answering these questions can help us decide whether today’s illegals would make good candidates for legal residency.

Advocates of legalization often refer to illegal immigrants as “undocumented.” Though the term is woefully insufficient, it is at least accurate — the federal government has no official records of illegal immigrants. So how do we know how many are here? By comparing records of legal immigration with the results of demographic surveys. The Department of Homeland Security knows how many foreign-born people enter the country legally each year. In nationally representative datasets, however, many more people say they are foreign-born than one would expect from the DHS data. These “residual” immigrants are in most cases illegal.

But do all illegal immigrants really respond (let alone respond truthfully) to government surveys? Could we be drastically undercounting them? No one knows for sure, but researchers do statistically adjust the illegal-immigrant count on the assumption that a certain percentage will give misinformation or avoid the surveys altogether.

The DHS estimate of 10.8 million illegal immigrants for 2009 is down from its peak of 11.8 million just two years earlier, and the trend is likely not a statistical anomaly. A poor economy and stepped-up enforcement by the Bush administration are the probable causes of the decrease.

Mexicans account for 62 percent of all illegals in the 2009 DHS data — an estimate that is higher than it was in 2000 (55 percent). An additional 12 percent come from three Central American countries — El Salvador, Guatemala, and Honduras. The countries outside Latin America from which the most illegals come are the Philippines, India, and South Korea, though these three countries combined make up only 6 percent of the total.

Unsurprisingly, illegal immigrants are disproportionately male (58 percent) and working-age (84 percent). About four of every five illegal immigrants entered within the last 20 years, and one in three came within the last decade. Beyond this information, however, the DHS does not know much about the illegal population. To flesh out the picture, we need to do some more statistical analysis.

Jeffrey Passel and other researchers at the Pew Hispanic Center have developed a technique that makes educated guesses about who may be an illegal immigrant in the Census Bureau’s Current Population Survey, which collects detailed demographic information. Survey respondents deemed “definitely” legal — e.g., government workers and welfare recipients — are discarded, and the remaining respondents are assigned a probability of being illegal based on several characteristics. If this process yields an illegal-immigrant population that doesn’t match the DHS estimates for illegals’ basic traits (average age, country of origin, etc.), then the researchers adjust the probabilities and start again.

The procedure is inherently imperfect, and it does produce some questionably optimistic results. For example, Pew reports that 35 percent of illegal-immigrant households own their own homes — this is only half the native rate, but it still sounds too high. Nevertheless, given the available data, Pew’s approach provides the best possible picture of illegal immigration.

The picture is not always a pretty one. In today’s economy, a high-school diploma is essentially the minimum educational standard, something achieved by over 90 percent of natives. However, nearly a third of illegal-immigrant adults have less than a ninth-grade education, and only slightly more than half graduated from high school. In fact, more than one of every five adult high-school dropouts in the U.S. is an illegal immigrant.

The lack of skills translates to low incomes and high poverty rates. The median income for illegal-immigrant-headed households is about $36,000. The poverty rate for illegal-immigrant adults is 21 percent, twice the native average. And compared with natives, more than four times as many illegals (59 percent) lacked health insurance in 2007.

When Pew compared illegals who had been in the U.S. for less than ten years with those who had stayed ten years or more, the latter group earned only $3,000 more annually. Perhaps legalization could improve economic mobility for immigrants over time, but their educational deficit is a daunting obstacle.

Legalization would add to our citizenry millions of people, most of them poor and less-educated, whose prospects for advancement are decidedly low. How one feels about this situation depends on several factors. From an economic perspective, low-skill immigrants offer cheap labor — a remarkable 94 percent of working-age male illegals are in the labor force. That makes goods and services less expensive for everyone, but it also depresses wages for the low-skill natives who have to compete with illegal immigrants for work.

The effect on our government’s fiscal situation is likewise a double-edged sword. Adding younger people to the workforce is a “bailout” of sorts for Medicare and Social Security, which rely on workers to fund retirees. As with most bailouts, however, low-skill immigration creates even worse problems over the long term; the benefits eventually owed to low-earning immigrants will be much greater than what they paid in.

Legalization will also have substantial cultural effects. Whether the U.S. can assimilate such a large number of poor and unskilled residents is an open question. Unlike newcomers from Europe a century ago, more recent low-skill immigrants have not joined the middle class in large numbers, even after several generations in the U.S. While the children of Hispanic immigrants do much better economically than their parents, progress abruptly stalls after the second generation, and third- and fourth-generation Hispanics make only about 80 percent of the average annual income earned by white Americans.

A middle-class lifestyle depends also on savings and investment. Families with a high net worth can own their homes, save for college, and cushion themselves against the ups and downs of the economy. According to Pew, the median net worth for white households in 2002 was $88,650. For U.S.-born Hispanic households, it was just $10,430.

Especially in our world of multiculturalism, La Raza, and ethnic studies, a large and persistent economic deficit between ethnic groups could easily fuel resentment and division. The extent to which people feel connected to their neighbors and communities is one of the best predictors of life satisfaction, and we should be careful not to weaken those ties.

When the legalization bill is introduced this summer, Americans should have an accurate understanding of its economic and social implications. We need to weigh the costs and benefits of absorbing a large cohort of low-skill individuals. Everyone, from Arizona to Minnesota, has a stake in this debate.