According to the 2000 Census, Johnson County, Illinois has a population of 12,878 people. Of those, 10,756 (84%) are White, 1,825 (14%) are Black, and 368 (3%) are Latino. However, 2,640 (or 21% of the 12,878 people) are not residents by choice but are people in prison.
Even though prisoners cannot participate in the local community, the Census Bureau nevertheless counts them as residents of the county where they are incarcerated.
A more accurate description would not include the prisoners. This would give Johnson County a population of 10,238 with a demographic that is 98% White, 0% Black, and 1% Latino.
The numbers for Whites, Blacks and Latinos may not add up to the total number because we have not included racial groups other than Whites and Blacks and because the Census Bureau considers "Latino" to be an ethnicity, not a race. Most of the people reported as being Latino are also counted as being White or Black.