America could come to resemble New York City by 2050, when one in five residents will have been born in another country if immigration flows hold at the current rate, a study published yesterday by the Pew Hispanic Center said. The study’s projections found that non-Hispanic whites will become a minority in less than 50 years, while both the Hispanic and Asian populations will have tripled in size.

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The findings suggest America is on a path to break immigration records set in 1890 and 1910, when immigrants accounted for 14% of the American population. The rate of immigration dropped sharply in the 1930s and 1940s after the Immigration Act of 1924 was passed, and spiked again in the 1990s.

By 2025, the current immigration boom could outstrip past increases, as immigrants are projected to total 15% of the population. By 2050, the number could be nearly 20%.

As the total population rises to 438 million in the next four decades, immigrants and their children will likely be responsible for 82% of the growth as the native population ages and its birth rate declines, the study by Jeffrey Passel and D’Vera Cohn, who based their findings on past and current trends, said.

If the projections play out, a 1% annual increase in the number of immigrants would allow America to keep pace with China and India, even as European countries see their populations decline further by mid-century.

The projected immigration boom prompted both warnings of dire consequences and sunny predictions of good times ahead from experts weighing in on both sides of the immigration debate.

“Where there’s immigration there’s growth, and where there’s growth there’s immigration,” a senior fellow at the New York-based Fiscal Policy Institute, David Dyssegaard Kallick, said.

In a recent study of immigrants in New York, Mr. Kallick reported that immigrants have been key to the state’s economic success.

A senior fellow at the Manhattan Institute, Heather MacDonald, suggested the rise in the Hispanic population could be problematic if new immigrants have trouble assimilating to American society.

“We’re sailing into uncharted territory,” she said. “It puts the assimilation project at great risk.” A senior economist at the Federal Reserve Bank of Dallas, Pia Orrenius, who advised the Bush administration on immigration, noted that the flow of immigrants from Latin America would likely include a smaller share of immigrants from Mexico as fertility rates decline there in the future, a projection also supported by the study’s authors.

“Demographically, it’s beneficial: We will not age as quickly,” she added of the study’s projections.

The numbers in the report suggested that baby boomers are likely to create a heavy strain on the American economy. While the immigration boom could help as immigrants expand their share of the working-age population, researchers also noted that the growing number of immigrants would be unlikely to overtake the growing number of people older than 65.

Among the other findings in the report: 19% of Americans will be immigrants by 2050, compared with 12% today; Latinos will make up almost a third of the nation’s population, compared with 14% now; the African-American population will grow by more than 50%, but will see its share of the population edge up only slightly, to a little more than 13%.

The report also found that the number of non-Hispanic whites will grow by 4% in the next 40 years, but they will see their share of the population drop to 47% of the total from 67% in 2005.