| | Decatur, IN | Fremont, OH | United States |
| Population | 9,630 | 15,954 | 329,725,481 |
| Female Population | 48.1% | 51.5% | 50.5% |
| Male Population | 51.9% | 48.5% | 49.5% |
| Median Age | 40.9 | 36.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 9,640 | 16,614 | 309,327,143 |
| Population - 2000 | 9,528 | 17,375 | 285,036,114 |
| Population - 1990 | 8,644 | 17,648 | 251,960,433 |
| Pop. 2000 to Now | 3.7% | -8.8% | 15.6% |
| Pop. 1990 to Now | 14.4% | -10.3% | 30.8% |
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| Population Density | 1,597.8 | 1,892.5 | 93.4 |
| Land Area | 6.0 | 8.4 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Decatur, IN | Fremont, OH | United States |
| Age 0 to 4 | 7.7% | 5.7% | 5.9% |
| Age 5 to 9 | 4.7% | 6.4% | 6.1% |
| Age 10 to 14 | 6.0% | 9.0% | 6.6% |
| Age 15 to 17 | 3.8% | 4.9% | 3.9% |
| Age 18 to 20 | 3.8% | 3.4% | 4.0% |
| Age 21 to 24 | 6.1% | 4.1% | 5.2% |
| Age 25 to 34 | 11.9% | 14.0% | 13.8% |
| Age 35 to 44 | 10.4% | 13.8% | 12.9% |
| Age 45 to 54 | 13.7% | 11.0% | 12.6% |
| Age 55 to 59 | 7.0% | 6.9% | 6.7% |
| Age 60 to 64 | 7.0% | 5.5% | 6.3% |
| Age 65 to 74 | 10.3% | 9.1% | 9.6% |
| Age 75 to 84 | 3.8% | 4.3% | 4.5% |
| Age 85 and over | 3.8% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Decatur, IN | Fremont, OH | United States |
| White | 89.2% | 73.4% | 59.4% |
| Black | 0.5% | 6.5% | 12.2% |
| Asian | 0.0% | 0.5% | 5.6% |
| Native American | 0.0% | 0.6% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.4% | 0.1% | 0.4% |
| Two or More Races | 1.4% | 3.5% | 3.2% |
| Hispanic | 8.6% | 15.4% | 18.4% |
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| Marriage & Family | | | |
| | Decatur, IN | Fremont, OH | United States |
| Married Population | 36.1% | 41.6% | 49.8% |
| Currently Married | 34.6% | 40.3% | 48.0% |
| Married but Separated | 1.6% | 1.2% | 1.8% |
| Single Population | 63.9% | 58.4% | 50.2% |
| Never Married | 29.8% | 34.7% | 33.8% |
| Divorced | 23.7% | 17.1% | 10.8% |
| Widowed | 10.3% | 6.7% | 5.6% |
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| Household Size | 2.21 | 2.37 | 2.60 |
| Households | 4,232 | 6,556 | 124,010,992 |
| Family Households | 2,221 | 3,662 | 80,755,759 |
| Married couple, w/children | 25.1% | 33.4% | 30.5% |
| Married couple, no children | 33.7% | 32.4% | 42.9% |
| Non Family Households | 2,011 | 2,894 | 43,255,233 |
| Single householder, w/children | 21.6% | 19.8% | 15.8% |
| Single householder, no children | 19.6% | 14.4% | 10.8% |