By Susan Heavey
WASHINGTON (Reuters) - A wave of immigrants is set to become the principal driver of U.S. population growth within 30 years, surpassing growth from births for the first time since the mid-1800's, federal government estimates show.
The swing toward growth from residents from abroad is expected between 2027 and 2038, the Census Bureau said in projections released on Wednesday.
By 2060, there could be 1.6 million new immigrants a year, compared with a natural population growth - the number of births exceeding deaths - of less than 900,000 annually, it said. (For a Reuters graphic, click on http://link.reuters.com/xug28t)
In addition to an influx of immigrants, the shift also results from the country's aging population and overall declining fertility rates, according to the agency, which tabulates much of the nation's demographic and economic data.
Thomas Mesenbourg, the Census Bureau's senior adviser, said the country has seen immigration surges before, "particularly during the great waves of the late 19th and early 20th centuries," but it has not outpaced births since at least 1850.
Exactly when the latest shift will occur is largely driven by the rate of immigration in coming years, which is closely tied to an immigration overhaul now before Congress.
The Census analysis comes as lawmakers are grappling with a plan to revise the nation's immigration laws not only to address the 11 million illegal immigrants but also other programs aimed at those seeking to enter legally.
Although it does not factor in potential changes from an overhaul of immigration laws, the agency's findings offer a fuller picture of what America will look like in a generation or two.
It based its estimates on past rates of migration, using high and low rates over the last nearly 70 years. But it is difficult to gauge what effects new immigration rules and other social, economic and political changes could have, said Census demographer Jennifer Ortman.
Changes in other countries have an effect, too, Ortman said.
At the low end of the range, 824,000 immigrants would be arriving annually by 2060 while higher rates could mean as many as 1.6 million by then, Census said, based on historical trends.
At current immigration rates, there would be 725,000 arriving each year through 2060.
(This story has been fixed to correct the figure in paragraph 11 to 1.6 million, not 1.6 billion)
(Reporting by Susan Heavey; Editing by Vicki Allen)