CHAMPAIGN — Population losses in Cook County and most of downstate Illinois slowed the growth in the state's population to 3.3 percent from 2000 through 2010, according to figures released Tuesday by the U.S. Census Bureau.

The state's population grew modestly from about 12.4 million to 12.8 million people, down from a growth rate of 8.7 percent the previous decade, the bureau said in a release of detailed statewide 2010 census data for Illinois. The overall population figures were made public in December.

Illinois' slowing growth will cost the state a congressional seat.

Much of the state's population growth was in counties that surround Chicago, such as Kendall County where the population more than doubled as well as downstate counties such as McLean and Champaign, with heavily white-collar economies.

And, while the state's populations of both whites and blacks decreased, the population of people who identified themselves as Hispanic grew at a sharp 32.5 percent rate.

"The state essentially owes its demographic sustainability to Latinos, Asians and immigrants," said Rob Paral, a Chicago-based demographer. "They permit the state to overcome a lot of depopulation."

The state had 2.03 million Hispanic residents in 2010, up from 1.53 million in 2000. In all, 15.8 percent of Illinois' residents identified themselves as Hispanic -- a category that can include whites, black and other racial categories.

The city of Chicago and Cook County both saw population drops through the decade, and those increases could have been sharper had the recession not slowed migration out of heavily urban areas since 2007.

Chicago's population decreased by nearly 7 percent since the 2000 Census. It's now nearly 2.7 million, down from nearly 2.9 million.

Cook County's population dwindled to just below 5.2 million, down by 3.4 percent since 2000.