NCW's illegal aliens: How we got the numbers

For purposes of this report, “unauthorized immigrant” refers to any non-U.S. citizen accused of entering the country without a visa or violating their conditions of residency, as charged by U.S. Immigration and Customs Enforcement.

A Wenatchee World analysis looked at the number of ICE detainers in the Okanogan County Jail and the Chelan County Regional Justice Center, which serves both Chelan and Douglas counties. (Similar numbers from Grant County were not available by press time.) The analysis does not distinguish between misdemeanor and felony arrests.

It also estimated the number of unauthorized immigrants in all three counties at about 4,360. This number was reached by comparing the Pew Hispanic Center’s figure for Washington’s 2009 undocumented population (about 200,000) with the 2006-2008 census count of foreign-born residents in NCW (about 17,400 people out of the three counties’ population of 146,000).

World graphic/Jared Johnson
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Counting the uncounted

The analysis assumes that the percentage of undocumented immigrants tracks with the percentage of foreign-born residents in each county. For instance, since Chelan County had 1.07 percent of Washington’s total foreign-born population in 2006-08 (8,523 people), it’s assumed that it also has 1.07 percent of the state’s 200,000 total unlawful immigrants (2,140).

However, since Pew’s 200,000 figure is the midpoint of an estimated range — 160,000 to 240,000 — the number of unauthorized immigrants in Chelan County could be as low as 1,712 or as high as 2,568. Thus local arrest rates in Chelan and Douglas could range from 10.2 to 15.3 percent of the total unauthorized population. In Okanogan County, the range could be 22 to 34 percent.

The newspaper’s method was vetted by Elizabeth Fussell, a sociologist at Washington State University who specializes in international immigration; and Anita Rocha, statistical programmer and data manager with the University of Washington’s Center for Studies in Demography and Ecology. Both said the method appears sound, but uncommon.

“You’ve delved into a place where demography is more art than science, because really we don’t have the numbers, and it just depends on what you can justify,” said Rocha.

Fussell said Pew chief demographer Jeffrey Passel is among the few researchers who try to tabulate unauthorized immigrant populations, since U.S. Census Bureau counts don’t track citizenship.

“What he does seems to be the best approach that we have, so we just take his numbers as pretty authorative,” Fussell said.

Passel wouldn’t comment on the Wenatchee World’s methodology, but in an e-mail he said of the jail statistics, “It is important to take into account age and sex structure. Unauthorized immigrant populations tend to have much higher shares of young adult males than other groups. Young adult males are much more likely to be arrested than other age-sex groups.”

Jorge Barón, executive director of the Northwest Immigrant Right Project, warned that NCW’s agricultural counties, relying heavily on immigrant field labor, may actually have a higher population of unauthorized immigrants than reflected in this analysis. That would lower the percentages of unauthorized residents who are arrested. And of course, immigrant populations — with valid visas and without — can shift with growing seasons.

“The assumption you’re making is that the undocumented population as a percentage of the total foreign-born population in the state is evenly distributed,” Barón said. “My sense is that that’s not quite the case, and there’s actually significant variation.”

http://www.wenatcheeworld.com/news/2010/oct/02/how-we-got-the-numbers/