Cook County welcomed 17,000 immigrants in 2012, expanding the population by .3 percent and retaining its position as the second most populated county in the nation, behind Los Angeles County, according to Thursday’s Census Bureau data.

Approximately 32,000 more residents left than moved in, mostly white and African-American, but Cook County saw gains, largely attributed to an increase in Hispanic immigrants and a high ratio of births over deaths. 

“Immigration is down, but it still is really, really key to maintaining the county’s population,” Chicago demographer Rob Paral of Rob Paral and Associates, told the Chicago Sun-Times.

DuPage, Lake, Will, Kane, McHenry and Will counties all saw gains of less than 1 percent in 2011.

Kendall County’s residents increased by 1.2 percent last year, slowing a bit since the last decade, but it is still the fastest-growing county in Illinois with a population over 10,000.

The Chicago metropolitan area, extending from Wisconsin to Indiana, keeping its position as the third most populated city in the nation, behind New York and Los Angeles. With 9.5 million people, Chicagoland’s population increased by 28,000.