| | Marlin, TX | Plano, TX | United States |
| Population | 5,512 | 282,181 | 329,725,481 |
| Female Population | 52.5% | 50.4% | 50.5% |
| Male Population | 47.6% | 49.6% | 49.5% |
| Median Age | 36.5 | 38.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 5,976 | 261,240 | 309,327,143 |
| Population - 2000 | 6,628 | 222,030 | 285,036,114 |
| Population - 1990 | 6,386 | 128,713 | 251,960,433 |
| Pop. 2000 to Now | -16.3% | 31.2% | 15.6% |
| Pop. 1990 to Now | -13.1% | 126.3% | 30.8% |
| space4 | | | |
| Population Density | 1,220.3 | 3,937.3 | 93.4 |
| Land Area | 4.5 | 71.7 | 3,531,905.4 |
| Water Area | 0.1 | 0.4 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Marlin, TX | Plano, TX | United States |
| Age 0 to 4 | 6.4% | 5.6% | 5.9% |
| Age 5 to 9 | 9.8% | 6.0% | 6.1% |
| Age 10 to 14 | 5.2% | 6.7% | 6.6% |
| Age 15 to 17 | 2.1% | 4.1% | 3.9% |
| Age 18 to 20 | 4.1% | 3.4% | 4.0% |
| Age 21 to 24 | 4.0% | 4.8% | 5.2% |
| Age 25 to 34 | 13.0% | 13.6% | 13.8% |
| Age 35 to 44 | 14.9% | 15.3% | 12.9% |
| Age 45 to 54 | 13.7% | 13.8% | 12.6% |
| Age 55 to 59 | 8.4% | 7.4% | 6.7% |
| Age 60 to 64 | 2.6% | 6.0% | 6.3% |
| Age 65 to 74 | 9.2% | 8.5% | 9.6% |
| Age 75 to 84 | 4.3% | 3.5% | 4.5% |
| Age 85 and over | 2.5% | 1.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Marlin, TX | Plano, TX | United States |
| White | 27.0% | 49.8% | 59.4% |
| Black | 45.9% | 8.5% | 12.2% |
| Asian | 0.3% | 22.2% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.5% | 0.4% |
| Two or More Races | 0.5% | 2.8% | 3.2% |
| Hispanic | 26.3% | 15.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Marlin, TX | Plano, TX | United States |
| Married Population | 33.7% | 58.1% | 49.8% |
| Currently Married | 27.3% | 57.0% | 48.0% |
| Married but Separated | 6.4% | 1.1% | 1.8% |
| Single Population | 66.3% | 41.9% | 50.2% |
| Never Married | 39.6% | 28.3% | 33.8% |
| Divorced | 18.2% | 9.8% | 10.8% |
| Widowed | 8.5% | 3.9% | 5.6% |
| space5 | | | |
| Household Size | 2.76 | 2.66 | 2.60 |
| Households | 1,767 | 106,022 | 124,010,992 |
| Family Households | 850 | 75,244 | 80,755,759 |
| Married couple, w/children | 23.9% | 38.4% | 30.5% |
| Married couple, no children | 30.0% | 42.0% | 42.9% |
| Non Family Households | 917 | 30,778 | 43,255,233 |
| Single householder, w/children | 24.6% | 10.3% | 15.8% |
| Single householder, no children | 21.5% | 9.3% | 10.8% |