While Chicago’s black population plunged dramatically in the last 10 years, according to the 2010 Census, the black population in Cook and the surrounding counties fell at half the pace.

African-Americans accounted for about 90 percent of Chicago’s 200,000-person population drop over the past 10 years, but the drop in the number of blacks in the six-county metropolitan region was on par with decline in the overall population.

The black population decline in the city “was so dramatic,” said community analyst Rob Paral.

The city’s black population dropped by 17 percent over the period, compared with an overall drop of 7 percent, based on analysis by Medill Reports of recently released census data. The rate of decline of the black population in Cook and the surrounding counties was 9 percent.

Some blamed the drop in the city on an error in the 2010 Census, but others disagree.

“I don’t believe it is due to an undercount,” Paral said, adding that the black population count is probably low, but likely as low this census as the last.

Paral, who advises large organizations on demographic issues, speculated that with a downturn in the labor market, blacks have left the state for jobs in the South. But while the city’s black population dropped by more than 180,000, the number in Illinois decreased by just 1 percent, or 23,000.

In Cook County and the surrounding counties, the population of blacks fell at the same rate as the decline in the general population.

Chicago’s black population dropped 4 percentage points, now accounting for 32 percent of the total. In the collar counties, the percentage of the population represented by blacks did not change by much more than a percentage point.

While DuPage County’s overall population fell by a quarter, its black population edged up 1 percent to more than 27,800.

The black population in nearby Lake County, Ind. slid 29 percent to about 87,300, greater than the decrease in any of the collar counties. The decline was similar to the drop in the total population of the county, which fell by a quarter in the past 10 years.

Hispanic population growing

And while the city’s overall population continues to shrink, the Latino community is nearing the size of both non-Hispanic white and black populations in the city.

According to recently released census data, the city saw a 7 percent drop in non-Hispanic whites and a 21 percent decrease in blacks since 2000; the Latino population increased by 3 percent to about 753,000. Now whites and blacks each make up 32 percent of the city’s population and Hispanics account for 29 percent.

Several factors are influencing the Hispanic population shift, said Paral.

Shifting populations can affect ward politics, especially because the City Council crafted current ward boundaries with Hispanics in mind. By law, the council must redraw the ward map by December, based on the populations identified in the 2010 Census.

That task is difficult, said Virginia Martinez, an attorney with the Mexican American Legal Defense and Education Fund, because you can draw lines a lot of different ways.

Martinez’s group advocates nationwide for Latinos. In 1992, the fund sued to overturn a newly drawn Chicago ward map, arguing that it dissected Hispanic populations in a way that deprived them of representation in City Hall.

During the drafting of the current map in 2001, the council crafted the 10th, 14th, 30th and 33rd wards to have Hispanic majorities, increasing the number of Latino-dominated wards to 11. Members of the fund said the change was not enough to reflect the increase in the Hispanic population.

Despite this year’s election of a new mayor, and turnover on the City Council, redistricting issues are the same, according to Martinez, as incumbents seek to hold on to their voting bloc.

“We always have the same concerns,” she said.