The sluggish pace puts the country “in a place we haven’t been in a very long time,” said William H. Frey, senior demographer at the Brookings Institution. “We don’t have that vibrancy that fuels the economy and people’s sense of mobility,” he said. “People are a bit aimless right now.”

Underlying the modest growth was an immigration level that was the lowest in 20 years. The net increase of immigrants to the United States for the year that ended in July was an estimated 703,000, the smallest since 1991, Mr. Frey said, when the immigrant wave that dates to the 1970s began to pick up pace. It peaked in 2001, when the net increase of immigrants was 1.2 million, and was still above 1 million in 2006. But it slowed substantially when the housing market collapsed, and the jobs associated with its boom that were popular among immigrants disappeared.

“Net immigration from Mexico is close to zero, and we haven’t seen that in at least 40 years,” said Jeffrey S. Passel, senior demographer at the Pew Hispanic Center. “We are in a very different kind of immigration situation.”

Mr. Passel said that the bulk of the reduction in recent years had been among illegal immigrants, adding that apprehensions at the border are just 20 percent of what they were a decade ago. (The Census Bureau does not ask foreign-born residents their status, but Mr. Passel believes the count includes most people here illegally. )

A lagging birth rate also contributed. Births in the United States declined precipitously during the recession and its aftermath, down by 7.3 percent from 2007 to 2010, according to Kenneth M. Johnson, the senior demographer at the Carsey Institute at the University of New Hampshire. There were slightly over four million births in the year that ended in July, the lowest since 1999.