What should the United States do about the 11 to 12 million undocumented immigrants currently living here? It’s a question that’s dominated recent immigration policy reform discussions, and may have been what ultimately derailed a bipartisan effort to pass new legislation this week.

Missing from much of the clamor, though, has been any consideration of just who the undocumented immigrants are. According to a report by the Pew Hispanic Center, undocumented immigrants:

• Account for about 5 percent, or 7.2 million, of the civilian labor force.
  
• Nearly a third of unauthorized workers worked in service jobs, and about a fifth worked in construction and extractive occupations.
  
• Undocumented workers also account for a large share of workers in certain job categories:
  
  • Farming (24%)
    
  • Cleaning (17%)
    
  • Food Preparation (12%)

• About 6.2 million people, or 56% of the unauthorized population, are from Mexico.
  
• Another 2.5 million, or 22%, come from the rest of Latin America, primarily Central America.
  
• Asian immigrants account for 13% of the undocumented.
  
• Male adults accounted for just under half (49%) of the unauthorized population. Female adults comprised 35%, and children were 18% of the total.
  
• As of 2005, there were 6.6 million families where either the head of the family or the spouse was an unauthorized migrant.
  
• Nearly two-thirds of the children living in unauthorized families are U.S. citizens by birth, an estimated 3.1 million children in 2005.

These are just numbers, of course. But when I hear people talk about illegal immigrants who slip across the border and consume social services, I think about the undocumented immigrants I met as a reporter, and the news articles I’ve read about their experiences. They’re far from the law-breaking freeloaders that some portray them to be.

To begin with, no one wants to leave their families and country. They leave for one reason: economic opportunity. It is possible for immigrants to earn in a day what they would make in a week in at home. The minimum wage in Mexico, for example, is about 55 pesos per day, which is less than $5. Of course, many people don’t earn the minimum wage, but much less.

Crossing the border is no easy undertaking. Many undocumented immigrants turn to smugglers, also known as coyotes, who charge several thousand dollars. Immigrants also fall prey to gangs who hold them for ransom and unscrupulous coyotes that take their money and abandon them in the desert.

With crackdowns along the California and Texas borders, undocumented immigrants have been funneled to Arizona’s remote desert, where many die of heat exhaustion. It’s a tragic and gruesome process, as one Arizona coroner describes it: stress overtaxes the body's cooling system, “the body temperature soars to 107 degrees, blood pressure plummets. Vital organs fail. Victims suffer cramps, nausea, and exhaustion. Some strip or go crazy. ‘Ultimately, they just sit down or collapse,’ ” coroner Bruce Parks told USA TODAY.

And even if they make it across the border, some are greeted at gunpoint by the Minutemen, a group of vigilantes who conduct armed patrols of the border.

Other undocumented immigrants don’t come through the desert, but by sea, though the results are just as deadly. In 1993, ten of 300 Chinese immigrants aboard the Golden Venture ship died when it was purposely run aground in the Rockaways, New York in June 1993. Fourteen others drowned off the coast of Guatemala in 1998 when a rickety boat off-loading them from a larger vessel capsized.

The woman responsible, Cheng Chui Ping, was not called a coyote but a “snakehead,” a smuggler who made $25,000 to $40,000 for each person she brought to the United States. Ping, who was sentenced to 35 years in prison, used a gang to make sure immigrants paid up, according to one news report.

Such “snakeheads” now charge up to $70,000, forcing many families into debt to pay for the trip. Half the fee is given to snakeheads as a down payment; the remainder is collected by smuggling networks when the immigrant "safely" arrives in the U.S., says Xiao-huang Yin, professor and chair of the American Studies Program at Occidental College. Newcomers often hold several jobs and work 80 hours a week to pay off their debts.

Horrific stories of immigrants suffocating to death after being packed into tiny trailers have also begun to emerge. In 2003, 19 migrants died of dehydration and suffocation after being trapped in a sealed tractor-trailer with at least 51 other people.

Once in the United States, the difficulties continue. It’s often said undocumented workers take the jobs no Americans want. But they also take the most dangerous jobs. Mexican workers in particular are more likely than others to be killed even when doing similarly risky work, a 2004 Associated Press investigation found. The accidental deaths, which kill one Mexican worker a day, are often preventable and grisly: workers are impaled, shredded in machinery and buried alive, the AP found.

Their undocumented status makes such workers the target of exploitation because many stay silent despite unsafe working conditions. Some farm workers in North Carolina, for example, were not given water, toilets or hand washing facilities in the field, a Legal Services of North Carolina attorney who helped migrant farm workers once told me. Workers were also sprayed with pesticides and made to work in freshly sprayed fields, she said.

NEXT: We take a look at the economics of undocumented immigration, and what the polls say Americans think about immigration.