Immigrants in the Hudson Valley make up 13 percent of the population but generate 16 percent of the economic output, says a new report from the Fiscal Policy Institute.

Census data from 2005-07 show that economic growth and immigration levels go hand in hand, said David Dyssegaard Kallick, director of the institute's Immigration Research Initiative.

"Where there was economic growth, there was growth in the immigrant share of the labor force," he said.

On the flip side, the institute has found, areas of slow economic growth like Pittsburgh, Cincinnatti and Cleveland had little growth in the immigrant share of the working population.

The newest study covered 15 counties in the region, from Westchester County to Warren County, north of Albany. Westchester accounts for almost a third of the region's total population, and more than half its immigrants.

Incomes and business revenue were used to calculate the immigrant share of economic growth. The study does not distinguish between illegal immigrants, legal residents or naturalized citizens.

Kallick said the findings run counter to assumptions that immigrants mostly work in very low-wage jobs, and show they demonstrate their presence in many different sectors. The economic data preceded the recession, but Kallick said the proportions would be unlikely to have shifted since then.

Immigrants are far more likely than American-born workers to be in farming and personal services, where foreign-born people hold a third of the jobs. But they are also slightly overrepresented in professional specialties like engineering, medicine and law.

One explanation for immigrants' outsize role in the economy: They are more likely than native-born Americans to be of working age.

"I think we ought to be careful as we get into immigration policy issues, at either the local or the national level, to make sure that we recognize the degree of contribution," Kallick said.

The contentious issue of immigration reform is likely to resurface Tuesday with the introduction of a bill by Rep. Luis Gutierrez, D-Ill., aimed at legalizing some undocumented immigrants.

Kallick sees potential for further growth with a legalization measure. "You would raise the level of economic contribution of undocumented immigrants if you made it possible for them to have legal status," he said.

The institute received funding from the Carnegie Corporation of New York and the Hagedorn Foundation.

For a similar study on 25 metropolitan areas, it received additional funding from the Service Employees International Union, Local 32BJ.