WASHINGTON – The population of America is on target to hit 300 million this fall.

Latinos are driving population growth. They accounted for almost half the increase last year, more than any other group. White non-Hispanics, who make up about two-thirds of the population, accounted for less than one-fifth of the increase.

When the population reached 200 million in 1967, there was no accurate tally of American Hispanics. The first effort to count Hispanics came in the 1970 census, and the results were dubious.

The Census Bureau counted about 9.6 million Latinos, a little less than 5% of the population. The bureau acknowledged that the figure was inflated in the Midwest and South because some who checked the box saying they were “Central or South American” thought that designation meant they were from central or southern America.

Most people in America did not have any neighbors from Central America or South America in the 1960s. The baby boom had just ended in 1964, and the country was growing through birth rates, not immigration, the Census Bureau’s associate director for demographic programs, Howard Hogan, said.

In 1967, there were fewer than 10 million in America who were born in other countries; not even one in 20. White non-Hispanics made up about 83% of the population.

Today, there are 36 million immigrants, about one in eight.

“We were much more of an insular society back then,” said William Frey, a demographer at the Brookings Institution, a Washington think tank. “It was much more of a white, middle-class, suburban society.”

As of midday yesterday, there were 299,061,199 people in America, according to the Census Bureau’s population clock. The estimate is based on annual numbers for births, deaths, and immigration, averaged throughout the year.

America adds a person every 11 seconds, according to the clock. A baby is born every eight seconds, someone dies every 13 seconds, and someone migrates to America every 30 seconds.

At that rate, the 300 millionth person in America will be born – or cross the border – in October, though bureau officials are wary of committing to a particular month because of the subjective nature of the clock.

Hispanics surpassed blacks as the largest minority group in 2001, and today make up more than 14% of the population.

America gained 2.8 million people last year – a little more than a million from immigration and about 1.7 million because births outnumbered deaths.

America is the third largest country in the world, behind China and India. America’s population is increasing by a little less than 1% a year, a pace that will keep it in third place for the foreseeable future, a demographer at the Population Reference Bureau, Carl Haub, said.

The world, with a population of 6.5 billion, is growing a little faster than 1% a year. By the time the American population hits 400 million, in the 2040s, white non-Hispanics will be but a bare majority. Hispanics are projected to make up close to one-quarter of the population, and blacks more than 14%. Asians will increase their share of the population to more than 7%.

Those percentages, however, are just projections. They are subject to big revisions, depending on immigration policy, cultural changes, and natural or manmade disasters.