| | Troy, OH | Decatur, IN | United States |
| Population | 26,093 | 9,630 | 329,725,481 |
| Female Population | 50.4% | 48.1% | 50.5% |
| Male Population | 49.6% | 51.9% | 49.5% |
| Median Age | 37.6 | 40.9 | 38.4 |
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| Population - 2010 | 25,230 | 9,640 | 309,327,143 |
| Population - 2000 | 21,999 | 9,528 | 285,036,114 |
| Population - 1990 | 19,478 | 8,644 | 251,960,433 |
| Pop. 2000 to Now | 20.3% | 3.7% | 15.6% |
| Pop. 1990 to Now | 35.9% | 14.4% | 30.8% |
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| Population Density | 2,171.2 | 1,597.8 | 93.4 |
| Land Area | 12.0 | 6.0 | 3,531,905.4 |
| Water Area | 0.2 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Troy, OH | Decatur, IN | United States |
| Age 0 to 4 | 6.2% | 7.7% | 5.9% |
| Age 5 to 9 | 7.1% | 4.7% | 6.1% |
| Age 10 to 14 | 7.6% | 6.0% | 6.6% |
| Age 15 to 17 | 4.7% | 3.8% | 3.9% |
| Age 18 to 20 | 4.2% | 3.8% | 4.0% |
| Age 21 to 24 | 3.4% | 6.1% | 5.2% |
| Age 25 to 34 | 12.4% | 11.9% | 13.8% |
| Age 35 to 44 | 15.1% | 10.4% | 12.9% |
| Age 45 to 54 | 13.5% | 13.7% | 12.6% |
| Age 55 to 59 | 5.0% | 7.0% | 6.7% |
| Age 60 to 64 | 5.3% | 7.0% | 6.3% |
| Age 65 to 74 | 8.3% | 10.3% | 9.6% |
| Age 75 to 84 | 5.6% | 3.8% | 4.5% |
| Age 85 and over | 1.5% | 3.8% | 1.9% |
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| Race | | | |
| | Troy, OH | Decatur, IN | United States |
| White | 85.2% | 89.2% | 59.4% |
| Black | 2.8% | 0.5% | 12.2% |
| Asian | 4.8% | 0.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.4% | 0.4% |
| Two or More Races | 3.9% | 1.4% | 3.2% |
| Hispanic | 3.3% | 8.6% | 18.4% |
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| Marriage & Family | | | |
| | Troy, OH | Decatur, IN | United States |
| Married Population | 52.9% | 36.1% | 49.8% |
| Currently Married | 51.9% | 34.6% | 48.0% |
| Married but Separated | 1.0% | 1.6% | 1.8% |
| Single Population | 47.1% | 63.9% | 50.2% |
| Never Married | 28.3% | 29.8% | 33.8% |
| Divorced | 12.4% | 23.7% | 10.8% |
| Widowed | 6.3% | 10.3% | 5.6% |
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| Household Size | 2.49 | 2.21 | 2.60 |
| Households | 10,359 | 4,232 | 124,010,992 |
| Family Households | 6,761 | 2,221 | 80,755,759 |
| Married couple, w/children | 37.3% | 25.1% | 30.5% |
| Married couple, no children | 37.9% | 33.7% | 42.9% |
| Non Family Households | 3,598 | 2,011 | 43,255,233 |
| Single householder, w/children | 16.7% | 21.6% | 15.8% |
| Single householder, no children | 8.1% | 19.6% | 10.8% |