| | Mars, PA | Derby, KS | United States |
| Population | 1,310 | 25,365 | 329,725,481 |
| Female Population | 55.2% | 50.6% | 50.5% |
| Male Population | 44.8% | 49.4% | 49.5% |
| Median Age | 55.4 | 35.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,699 | 22,524 | 309,327,143 |
| Population - 2000 | 1,746 | 17,807 | 285,036,114 |
| Population - 1990 | 1,713 | 14,699 | 251,960,433 |
| Pop. 2000 to Now | -7.9% | 41.2% | 15.6% |
| Pop. 1990 to Now | -6.1% | 71.1% | 30.8% |
| space4 | | | |
| Population Density | 2,781.3 | 2,473.4 | 93.4 |
| Land Area | 0.5 | 10.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Mars, PA | Derby, KS | United States |
| Age 0 to 4 | 1.5% | 5.5% | 5.9% |
| Age 5 to 9 | 3.8% | 8.3% | 6.1% |
| Age 10 to 14 | 5.5% | 9.1% | 6.6% |
| Age 15 to 17 | 2.7% | 4.2% | 3.9% |
| Age 18 to 20 | 1.4% | 3.3% | 4.0% |
| Age 21 to 24 | 7.1% | 5.2% | 5.2% |
| Age 25 to 34 | 10.6% | 12.9% | 13.8% |
| Age 35 to 44 | 6.7% | 14.6% | 12.9% |
| Age 45 to 54 | 8.6% | 10.1% | 12.6% |
| Age 55 to 59 | 12.7% | 7.1% | 6.7% |
| Age 60 to 64 | 12.7% | 4.9% | 6.3% |
| Age 65 to 74 | 11.6% | 7.7% | 9.6% |
| Age 75 to 84 | 10.6% | 5.1% | 4.5% |
| Age 85 and over | 4.5% | 2.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Mars, PA | Derby, KS | United States |
| White | 94.8% | 82.3% | 59.4% |
| Black | 2.4% | 1.2% | 12.2% |
| Asian | 0.0% | 1.3% | 5.6% |
| Native American | 0.0% | 0.7% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.0% | 5.7% | 3.2% |
| Hispanic | 2.7% | 8.7% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Mars, PA | Derby, KS | United States |
| Married Population | 29.1% | 60.3% | 49.8% |
| Currently Married | 29.1% | 59.1% | 48.0% |
| Married but Separated | 0.0% | 1.1% | 1.8% |
| Single Population | 70.9% | 39.7% | 50.2% |
| Never Married | 35.0% | 23.4% | 33.8% |
| Divorced | 19.9% | 10.6% | 10.8% |
| Widowed | 16.0% | 5.8% | 5.6% |
| space5 | | | |
| Household Size | 1.98 | 2.54 | 2.60 |
| Households | 615 | 9,953 | 124,010,992 |
| Family Households | 267 | 6,783 | 80,755,759 |
| Married couple, w/children | 27.0% | 37.1% | 30.5% |
| Married couple, no children | 33.7% | 43.1% | 42.9% |
| Non Family Households | 348 | 3,170 | 43,255,233 |
| Single householder, w/children | 9.0% | 10.8% | 15.8% |
| Single householder, no children | 30.3% | 9.0% | 10.8% |