According to the 2000 Census, Mercer County, New Jersey has a population of 350,761 people. Of those, 240,206 (69%) are White, 69,502 (20%) are Black, and 33,898 (9%) are Latino. However, 4,182 (or 1% of the 350,761 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 Mercer County a population of 346,579 with a demographic that is 69% White, 19% Black, and 10% 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.