The United States population grew only 0.72 percent last year, to 316,128,839 in July from 313,873,685 a year earlier, according to figures released Monday by the Census Bureau.

It is the lowest rate in more than seven decades, said William Frey, a demographer at the Brookings Institution in Washington.

"The census projections to 2060 have us going down to half a percent because we're an older population, and aging populations don't grow so much," Mr. Frey said. "If we have very sharp declines in growth, that takes a bite out of the economy."

For the time being, New York remains the nation's third most populous state, after California and Texas — but its lead over Florida narrowed to less than 100,000 people over the last year, according to the census figures. If New York's tepid growth rate and Florida's rapid one continue over the next year, Florida will pull ahead.

The nation's long shift to the South and the West is continuing. In the Midwest and the Northwest, the population edged up by less than half a percent, while in the West and the South the population grew by nearly 1 percent. There was strong growth not just in California, Texas and Florida, but also in Arizona, Colorado, Utah and Washington.

The largest population increases over the year were in Texas (387,397 people), California (332,643) and Florida (232,111). New York, which added 75,002 people, ranked ninth. California this year became the first state to top 38 million residents, with a population of 38,332,521.

Two small states, Maine and West Virginia, lost population over the year. And Puerto Rico lost about 1 percent of its residents.

In percentages, the biggest gainer was North Dakota, which grew by 3.14 percent because of the oil and gas boom.

It was followed by the District of Columbia (2.06 percent), Utah (1.61 percent) Colorado (1.52 percent) and Texas (1.49 percent).

New York ranked 32nd, at 0.38 percent, and New Jersey 33rd, at 0.36 percent. Connecticut ranked 44th, at 0.12 percent.

In a separate release, the Census Bureau projected that on Jan. 1, the United States population would be 317,297,938, a 0.7 percent increase from Jan. 1, 2013.

In January 2014, the bureau said, one birth is expected every eight seconds in the United States, and a death every 12 seconds.

The projected world population on Jan. 1, 2014, is 7,137,577,750, an increase of 77,630,563, or 1.1 percent, from Jan. 1, 2013.

In January 2014, 4.3 births and 1.8 deaths are expected worldwide every second. India added 15.6 million people over the one-year period. It led all countries, followed by China, Nigeria, Pakistan and Ethiopia.