What keeps America's population clock ticking are people like Dominic Paz.
On a busy day running Alpha Taxi in Lawrenceville, Ga., he flips through a wad of $10s and $20s as he chats in both English and Spanish on two cellphones while dispatching cabs from a croaking CB radio. An immigrant from Honduras, Mr. Paz points to the blur of cars passing his home base – a bench at a strip mall that caters to Hispanics. "Two, three years ago, it was nothing like this, nothing."
Lawrenceville has grown 27 percent in five years, and a big reason is immigration. In all of Gwinnett County, the number of foreign-born residents has nearly doubled in that time. "It's 80 percent Hispanic," Paz says. "There's a brown face everywhere you look."
While growth is slowing almost everywhere in the developed world, three factors are powering the US population toward the 300 million mark. Couples are having enough babies to replace themselves. People are living longer. And the biggest reason: Immigration to the US has sharply increased in recent decades.
Immigration is not only boosting America's numbers, it's changing the face of the country. That 300 millionth new person, expected in a few weeks, is just as likely to fly in from China (or wade across the Rio Grande from Mexico) as he or she is to be born here. To put it another way: Every 31 seconds another person from abroad is added to the US population roll.
The rise in newcomers – nearly quadruple the number in 1970 – has fueled a widespread backlash against illegal immigrants. That's half the story. The less familiar but also important trend is the influx of highly skilled workers and highly motivated entrepreneurs who have helped the US economy grow.
While 23 percent of the nation's cooks and 20 percent of its janitors were immigrants in 2000, 27 percent of new computer-software engineers were also immigrants, according to a recent Migration Policy Institute study.
Indeed, the more technically educated the group, the more likely immigrants are to be overrepresented in it. While the foreign born make up 15 percent of the overall workforce, according to the 2000 census, they constitute approximately 17 percent of those with a bachelor's degree in science and engineering occupations, 29 percent of those with a master's degree, and 39 percent of those with a doctoral degree.
Already, 1 in 5 US doctors is foreign born, as are 2 in 5 medical scientists, 1 in 5 computer specialists, 1 in 6 people in engineering or science occupations, 1 in 4 astronomers, physicists, chemical, and material scientists, and 1 in 6 biological scientists, according to another Migration Policy Institute study.
"Plainly, high-skilled immigrants are a critical resource for the knowledge-driven economy and play an important role in the country's global dominance in science and engineering and its leadership in technology," write the study's authors, Columbia University economist Neeraj Kaushal and Migration Policy Institute vice president Michael Fix.
In some ways, the nation's big population milestones – America at 100 million, 200 million, and 300 million – bookend the ebb and flow of immigrants.
In 1910, at the height of the last immigration boom and just five years shy of reaching the 100 million mark, nearly 15 percent of Americans were foreign born. For the next 60 years, that percentage dropped steadily, down to less than 5 percent.
But in 1970, not long after the US population reached 200 million, the figure began to climb again. Today, it's back up to over 12 percent.
The result: a smaller share of immigrants than in 1910, but a far greater number. Estimates put the total near 35 million (legal and illegal). That's 2-1/2 times as many immigrants as there were in 1910.
There's another difference: Whereas the early 1900s saw thousands of Europeans arriving through Ellis Island, then filling up New York's tenement buildings or pushing on to become factory workers, farmers, and shopkeepers in the Midwest, most immigrants today come from Latin America or Asia. As of 2000, 52 percent were from Latin America, 26 percent from Asia, and only 19 percent from Europe.
Immigrants are also spreading out, changing the complexion of corners of the country unaccustomed to waves of foreign-speaking newcomers.
The South, in particular, has seen rapid change: Eastern European dealers at casinos in Mobile, Ala.; Korean shopkeepers in Atlanta; Mexican Christmas tree harvesters on North Carolina's Appalachian slopes.
Some of the states with the fastest- growing immigrant populations lie in the South. Some parts of the region have seen up to 300 percent growth in immigrant populations since 1990.
Such growth is evident in Lawrenceville, the seat of Gwinnett County. Planners see a vibrant future. The county school system has set up a special language center to test new students. There are enough new immigrant children here each year to fill a new school, as they make up about 1,500 of the 7,000 additional students flowing into the school district each year.
But there's another side. County commissioners earlier this year banned mobile taco stands for being too trashy looking. This year, the Georgia legislature passed the Security and Immigration Compliance Act, one of the nation's toughest bills to curb illegal immigration.
The law caused a ripple of fear, says Paz in Lawrenceville. As he talks to one Mexican woman grabbing a ride, she says she'll go to Canada when the law takes effect next summer. "People are afraid," says Paz.
So are many American workers, who fear that immigrants will take their jobs. The data are inconclusive.
The Pew Hispanic Center recently used US census information to compare increases in the foreign-born population with employment opportunities at the state level. It looked at two periods in particular: the boom years of the 1990s and the downturn and recovery since 2000.
The bottom line, according to Pew associate research director Rakesh Kochhar: "The size of the foreign-born workforce in a state appears to have no relationship to the employment prospects for native-born workers."
In general, other experts agree.
"While the number of immigrants is very large, the impact on the overall economy is very small," says Steven Camarota, director of research for the Center for Immigration Studies.
But, he added in recent testimony before the House Judiciary Committee, "While the impact on the economy as a whole may be tiny, the effect on some Americans, particularly workers at the bottom of the labor market, may be quite large."
That's a major concern for those who want to see the federal government change what they see as too-liberal immigration policies and not enough border security.
"It certainly has resulted in the importation of labor substitutes for a wide variety of American workers, with the result that we're widening the wage gap for less skilled workers who've seen real wages declining," says Dan Stein, executive director of the Federation for American Immigration Reform (FAIR) in Washington. "Substitutes erode bargaining leverage and decrease offered wages. Supply and demand works here as everywhere else."
Even the number of illegal immigrants is in dispute. About 30 percent of immigrants – an estimated 11 million – are here illegally, according to most government and private sources. That figure is believed to be growing by some 500,000 a year, according to the US Citizenship and Immigration Services (formerly the Immigration and Naturalization Service).
But one research team posited last year that as many as 20 million illegal immigrants may be living in the US today. Robert Justich and Betty Ng of Bear Stearns, a global investment banking, securities trading, and brokerage firm, based their conclusion on a study of public school enrollment, language-proficiency programs, building permits, and the significant amount of money being sent home by undocumented workers.
One of their conclusions: "Four [million] to six million jobs have shifted to the underground market as small businesses take advantage of the vulnerability of illegal residents."
There's another kind of vulnerability as well. In an investigative report this month, the Chicago Tribune found that illegal immigrants face disproportionate injuries and fatalities – often unreported – doing hazardous jobs like meat-cutting and dry-cleaning.
About half the total US population increase these days is Hispanic, according to the US Census Bureau, making Hispanics the largest and fastest-growing racial or ethnic minority. Part of that rise is children born to Hispanics already in the country. The rest comes from immigration. Fifty-seven percent of those newcomers are from Mexico, and another 24 percent are from other Latin American countries, according to the Pew Hispanic Center, a nonpartisan research group in Washington.
On average, Hispanics in the US are considerably younger than the population as a whole: Their median age is about 27 compared with about 36 for the country generally. That means that as older non-Hispanics retire, there will be relatively more workers to pay into Social Security. It also means more Hispanics in the future. About one-third of them are under 18 – just entering the years when they'll have children of their own.
"People come for a place to raise their kids, where there's a future," says Marcel Cueva, a Lawrenceville cab driver who came from the Dominican Republic 18 years ago and recently became a US citizen.
"Other places like New York have become too expensive," says Mr. Cueva, who has four children and soon may be joined here by his father. "You can make money, but the money is gone. Here you can keep some of it."
The fact that the US has recently become home to an extraordinary number of immigrants also may indicate a new direction for the country as it moves on toward 400 million people, probably sometime in the middle of the century.
"It says that we're going to be a country that is more outwardly reaching to the rest of the world, that we'll be more multicultural than we've been in the recent past," says William Frey, a demographer at the University of Michigan and the Brookings Institution think tank in Washington.
• Next Tuesday: The environmental imprint of 300 million.