| | Clayton, OH | Ellicott City, MD | United States |
| Population | 13,246 | 74,432 | 329,725,481 |
| Female Population | 50.3% | 51.2% | 50.5% |
| Male Population | 49.7% | 48.8% | 49.5% |
| Median Age | 45.3 | 41.8 | 38.4 |
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| Population - 2010 | 13,240 | 64,970 | 309,327,143 |
| Population - 2000 | 13,347 | 56,397 | 285,036,114 |
| Population - 1990 | 713 | 41,396 | 251,960,433 |
| Pop. 2000 to Now | -0.9% | 34.1% | 15.6% |
| Pop. 1990 to Now | 1,756.0% | 82.6% | 30.8% |
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| Population Density | 715.8 | 2,484.0 | 93.4 |
| Land Area | 18.5 | 30.0 | 3,531,905.4 |
| Water Area | 0.1 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Clayton, OH | Ellicott City, MD | United States |
| Age 0 to 4 | 7.9% | 5.1% | 5.9% |
| Age 5 to 9 | 6.7% | 7.0% | 6.1% |
| Age 10 to 14 | 5.0% | 8.7% | 6.6% |
| Age 15 to 17 | 3.6% | 5.2% | 3.9% |
| Age 18 to 20 | 1.8% | 3.2% | 4.0% |
| Age 21 to 24 | 2.6% | 3.5% | 5.2% |
| Age 25 to 34 | 12.3% | 8.0% | 13.8% |
| Age 35 to 44 | 9.7% | 14.7% | 12.9% |
| Age 45 to 54 | 11.6% | 15.3% | 12.6% |
| Age 55 to 59 | 8.5% | 7.0% | 6.7% |
| Age 60 to 64 | 7.4% | 5.8% | 6.3% |
| Age 65 to 74 | 13.9% | 10.2% | 9.6% |
| Age 75 to 84 | 6.9% | 4.3% | 4.5% |
| Age 85 and over | 2.1% | 2.0% | 1.9% |
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| Race | | | |
| | Clayton, OH | Ellicott City, MD | United States |
| White | 62.8% | 52.6% | 59.4% |
| Black | 28.8% | 8.1% | 12.2% |
| Asian | 1.6% | 29.6% | 5.6% |
| Native American | 0.5% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.2% | 0.6% | 0.4% |
| Two or More Races | 4.6% | 4.4% | 3.2% |
| Hispanic | 1.6% | 4.6% | 18.4% |
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| Marriage & Family | | | |
| | Clayton, OH | Ellicott City, MD | United States |
| Married Population | 57.3% | 64.0% | 49.8% |
| Currently Married | 55.0% | 63.1% | 48.0% |
| Married but Separated | 2.3% | 1.0% | 1.8% |
| Single Population | 42.7% | 36.0% | 50.2% |
| Never Married | 24.7% | 24.7% | 33.8% |
| Divorced | 11.4% | 6.4% | 10.8% |
| Widowed | 6.6% | 4.9% | 5.6% |
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| Household Size | 2.47 | 2.77 | 2.60 |
| Households | 5,308 | 26,737 | 124,010,992 |
| Family Households | 3,780 | 20,460 | 80,755,759 |
| Married couple, w/children | 21.6% | 45.2% | 30.5% |
| Married couple, no children | 53.9% | 40.5% | 42.9% |
| Non Family Households | 1,528 | 6,277 | 43,255,233 |
| Single householder, w/children | 16.8% | 8.5% | 15.8% |
| Single householder, no children | 7.6% | 5.8% | 10.8% |