| | Mayfield, KY | Portsmouth, OH | United States |
| Population | 10,041 | 18,369 | 329,725,481 |
| Female Population | 53.8% | 53.3% | 50.5% |
| Male Population | 46.2% | 46.7% | 49.5% |
| Median Age | 36.8 | 36.5 | 38.4 |
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| Population - 2010 | 10,064 | 20,168 | 309,327,143 |
| Population - 2000 | 10,349 | 20,909 | 285,036,114 |
| Population - 1990 | 9,935 | 22,676 | 251,960,433 |
| Pop. 2000 to Now | -6.4% | -5.6% | 15.6% |
| Pop. 1990 to Now | -2.5% | -12.9% | 30.8% |
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| Population Density | 1,372.9 | 1,711.3 | 93.4 |
| Land Area | 7.3 | 10.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.3 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mayfield, KY | Portsmouth, OH | United States |
| Age 0 to 4 | 6.3% | 5.8% | 5.9% |
| Age 5 to 9 | 7.4% | 6.6% | 6.1% |
| Age 10 to 14 | 9.4% | 6.0% | 6.6% |
| Age 15 to 17 | 2.9% | 3.9% | 3.9% |
| Age 18 to 20 | 2.3% | 5.0% | 4.0% |
| Age 21 to 24 | 6.2% | 6.8% | 5.2% |
| Age 25 to 34 | 13.3% | 14.0% | 13.8% |
| Age 35 to 44 | 13.7% | 11.6% | 12.9% |
| Age 45 to 54 | 6.5% | 9.5% | 12.6% |
| Age 55 to 59 | 5.4% | 6.7% | 6.7% |
| Age 60 to 64 | 8.0% | 6.1% | 6.3% |
| Age 65 to 74 | 9.5% | 10.2% | 9.6% |
| Age 75 to 84 | 5.7% | 6.0% | 4.5% |
| Age 85 and over | 3.2% | 1.7% | 1.9% |
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| Race | | | |
| | Mayfield, KY | Portsmouth, OH | United States |
| White | 72.5% | 85.3% | 59.4% |
| Black | 12.3% | 6.4% | 12.2% |
| Asian | 0.6% | 1.2% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.4% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 4.1% | 4.2% | 3.2% |
| Hispanic | 10.2% | 2.8% | 18.4% |
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| Marriage & Family | | | |
| | Mayfield, KY | Portsmouth, OH | United States |
| Married Population | 46.8% | 35.8% | 49.8% |
| Currently Married | 44.9% | 32.5% | 48.0% |
| Married but Separated | 1.9% | 3.4% | 1.8% |
| Single Population | 53.2% | 64.2% | 50.2% |
| Never Married | 25.6% | 41.0% | 33.8% |
| Divorced | 18.7% | 14.4% | 10.8% |
| Widowed | 8.9% | 8.8% | 5.6% |
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| Household Size | 2.32 | 2.35 | 2.60 |
| Households | 4,215 | 7,259 | 124,010,992 |
| Family Households | 2,309 | 3,950 | 80,755,759 |
| Married couple, w/children | 33.7% | 22.2% | 30.5% |
| Married couple, no children | 40.3% | 33.4% | 42.9% |
| Non Family Households | 1,906 | 3,309 | 43,255,233 |
| Single householder, w/children | 18.1% | 28.5% | 15.8% |
| Single householder, no children | 7.9% | 15.8% | 10.8% |