WASHINGTON — The wave of immigrants entering America slowed dramatically last year as the economy faltered and the government stepped up enforcement of immigration laws.

The nation added about a half million immigrants in 2007, down from more than 1.8 million the year before, according to estimates being released Tuesday by the Census Bureau.

“The U.S. is still a beacon for many people who want to come here for all kinds of reasons,” a demographer at the Brookings Institution who analyzed the numbers, William Frey, said. “But what this shows is that the economy plays a big part in it.”

America has added an average of about a million immigrants a year since 1990, including those in the country legally and illegally.

At more than 38 million, the number of immigrants in America is now at an all-time high. Immigrants made up 12.6% of the population in 2007, the largest share since 1920, when America was nearing the end of its last immigration boom, one that brought millions of people from Europe to America.

That wave of immigrants ended with the Great Depression and the onset of World War II.

The immigration figures released today were from the 2007 American Community Survey, the government’s annual survey of about 3 million households. The survey, which is replacing the long form from the 10-year census, yields reams of demographic, social and economic data about the nation.

Because the estimates come from a survey, each includes a margin of sampling error that makes year-to-year comparisons inexact. Annual immigration changes for many states and cities were within the margins of error, but the national trend was statistically significant: The nation’s immigration boom slowed substantially in 2007.

Fourteen states showed declines in the estimated number of immigrants from 2006 to 2007.Several major cities also posted decreases. Other cities continued to show gains.

“Immigrants have always come to the United States for jobs, but before they went to big immigration magnets to be with family or other immigrants,” Mr. Frey said. “Now the geography of where these people move is much more tied to the economy than ever before.”

Much of America experienced a housing boom in the first half of the decade, providing jobs that attracted immigrants. The housing bubble burst last year, sending housing markets tumbling and contributing to a slumping economy that some economists believe is in recession.

The Census Bureau’s estimates for immigrants include those in America legally and illegally because the agency does not ask about legal status. Government and private estimates put the number of illegal immigrants in the U.S. at about 12 million.

A little more than half of America’s immigrants are from Latin America and about a quarter are from Asia. About 13% are from Europe and 4 percent from Africa.

The latest immigration boom has sparked political and social turmoil in many communities unaccustomed to large influxes of foreigners. About one in five American residents spoke a language other than English at home in 2007, about the same share as a year before.

The issue, however, has been muted in this year’s presidential election in part because both Senator McCain and Senator Obama support comprehensive immigration packages that include increased enforcement and an eventual path to citizenship for many illegal immigrants.

Mr. Obama and Mr. McCain are not talking much about immigration reform — at least not in English. Both, however, are running Spanish-language TV ads accusing the other of derailing comprehensive immigration packages supported by many Hispanics.

Voters say other issues are more important to them than immigration policy, including the economy, gas prices, and education, according to the latest AP-Yahoo News poll.