| | Plainfield, NJ | Olathe, KS | United States |
| Population | 54,183 | 140,339 | 329,725,481 |
| Female Population | 47.6% | 50.2% | 50.5% |
| Male Population | 52.4% | 49.8% | 49.5% |
| Median Age | 34.1 | 35.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 49,622 | 126,253 | 309,327,143 |
| Population - 2000 | 47,829 | 92,962 | 285,036,114 |
| Population - 1990 | 46,567 | 63,352 | 251,960,433 |
| Pop. 2000 to Now | 4.6% | 52.4% | 15.6% |
| Pop. 1990 to Now | 7.4% | 123.6% | 30.8% |
| space4 | | | |
| Population Density | 9,092.6 | 2,277.3 | 93.4 |
| Land Area | 6.0 | 61.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.8 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Plainfield, NJ | Olathe, KS | United States |
| Age 0 to 4 | 7.2% | 6.5% | 5.9% |
| Age 5 to 9 | 7.9% | 8.3% | 6.1% |
| Age 10 to 14 | 7.5% | 8.0% | 6.6% |
| Age 15 to 17 | 4.4% | 4.8% | 3.9% |
| Age 18 to 20 | 3.5% | 3.5% | 4.0% |
| Age 21 to 24 | 5.4% | 4.2% | 5.2% |
| Age 25 to 34 | 15.5% | 12.9% | 13.8% |
| Age 35 to 44 | 13.9% | 15.9% | 12.9% |
| Age 45 to 54 | 12.9% | 13.5% | 12.6% |
| Age 55 to 59 | 5.4% | 5.8% | 6.7% |
| Age 60 to 64 | 5.1% | 4.7% | 6.3% |
| Age 65 to 74 | 7.3% | 7.5% | 9.6% |
| Age 75 to 84 | 2.9% | 3.2% | 4.5% |
| Age 85 and over | 1.1% | 1.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Plainfield, NJ | Olathe, KS | United States |
| White | 8.8% | 74.9% | 59.4% |
| Black | 35.9% | 5.8% | 12.2% |
| Asian | 1.0% | 4.2% | 5.6% |
| Native American | 0.1% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.6% | 0.4% | 0.4% |
| Two or More Races | 1.5% | 3.2% | 3.2% |
| Hispanic | 51.3% | 11.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Plainfield, NJ | Olathe, KS | United States |
| Married Population | 38.7% | 59.4% | 49.8% |
| Currently Married | 36.6% | 58.4% | 48.0% |
| Married but Separated | 2.1% | 1.0% | 1.8% |
| Single Population | 61.3% | 40.6% | 50.2% |
| Never Married | 50.2% | 27.3% | 33.8% |
| Divorced | 7.2% | 9.7% | 10.8% |
| Widowed | 3.9% | 3.6% | 5.6% |
| space5 | | | |
| Household Size | 3.17 | 2.77 | 2.60 |
| Households | 16,693 | 50,141 | 124,010,992 |
| Family Households | 12,076 | 37,203 | 80,755,759 |
| Married couple, w/children | 27.6% | 40.9% | 30.5% |
| Married couple, no children | 27.0% | 40.3% | 42.9% |
| Non Family Households | 4,617 | 12,938 | 43,255,233 |
| Single householder, w/children | 29.3% | 12.3% | 15.8% |
| Single householder, no children | 16.1% | 6.4% | 10.8% |