As the United Nations observes World Population Day July 11, new statistics show the United States is approaching a major population milestone. The Census Bureau predicts the United States population will reach 300 million people sometime in October.
The clock on the Census Bureau's website adds one person to the U.S. population count every 11 seconds, a growth rate about the same as China's.
The United States is the fastest growing industrialized nation in the world, adding about one percent or 2.8 million people each year.
Demographer Andrew Beveridge of New York's Queens College says immigration is the main engine of U.S. population growth.
"The major factor that has made it so that the United States population continues to grow is immigration, and coupled with that is the children of immigrants," he said.
The estimated 36 million immigrants in the United States are spurring the growth both in their birth rate and in their arrival rate. Demographers say one new immigrant arrives every 30 seconds. Most are Hispanic.
Global population pressures are one reason for rising immigration rates. The world total of 6.5 billion people rises by 76 million every year and nearly all those new people are in the developing world.
Declining birth rates in Europe are causing concern. According to data from the Central Intelligence Agency, on average women must have two children each for a society to replenish itself and Albania is the only country in Europe that has a fertility rate of more than two.
Professor Beveridge says that unlike some European countries that have discouraged immigration, the United States has a steady supply of people able to support the nation's infrastructure and services.
"The fact that immigrants are continuing to come in, you do not get into the situation that a number of European countries have gotten into, where they actually very very few younger people," he said. "And so when you have that, you do not really have people who can work. In that situation, the population ages, ages, and ages and you do not have enough younger people to work and what that leads to is you can't fund the retirement system."
Population experts predict the United States will increase to 420 million people by 2050.
China, with its one child policy, is expected to maintain a stable population over the next four decades as India surpasses it as the most world's most populous country. The United States is expected to remain third.
Although this October will mark a major increase in the U.S. population, Beveridge says unless immigration continues at its current rate, the United States will face the same predicament as other nations in the West.
"Right now, younger people who do not marry, who do not have kids or maybe just have one kid is really growing," he said. "And that is exactly what has happened in Europe and I think that if we follow that trend, it is a much more disturbing trend than accommodating whatever it is, 20 or 30 million immigrants."
The Census Bureau's clock will reach the October milestone shortly before Congressional mid-term elections, in which illegal immigration will likely be an important issue.