| | Tiffin, OH | Dover, NH | United States |
| Population | 17,882 | 32,599 | 329,725,481 |
| Female Population | 51.1% | 50.7% | 50.5% |
| Male Population | 48.9% | 49.3% | 49.5% |
| Median Age | 35.5 | 36.2 | 38.4 |
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| Population - 2010 | 17,876 | 30,038 | 309,327,143 |
| Population - 2000 | 18,135 | 26,884 | 285,036,114 |
| Population - 1990 | 18,604 | 25,042 | 251,960,433 |
| Pop. 2000 to Now | -4.3% | 20.7% | 15.6% |
| Pop. 1990 to Now | -6.7% | 29.6% | 30.8% |
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| Population Density | 2,603.7 | 1,219.6 | 93.4 |
| Land Area | 6.9 | 26.7 | 3,531,905.4 |
| Water Area | 0.1 | 2.3 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Tiffin, OH | Dover, NH | United States |
| Age 0 to 4 | 4.3% | 6.0% | 5.9% |
| Age 5 to 9 | 5.2% | 3.7% | 6.1% |
| Age 10 to 14 | 5.8% | 4.3% | 6.6% |
| Age 15 to 17 | 3.4% | 3.1% | 3.9% |
| Age 18 to 20 | 11.8% | 1.9% | 4.0% |
| Age 21 to 24 | 6.6% | 9.4% | 5.2% |
| Age 25 to 34 | 12.3% | 19.2% | 13.8% |
| Age 35 to 44 | 10.2% | 13.3% | 12.9% |
| Age 45 to 54 | 11.6% | 11.5% | 12.6% |
| Age 55 to 59 | 5.1% | 6.5% | 6.7% |
| Age 60 to 64 | 5.8% | 4.8% | 6.3% |
| Age 65 to 74 | 8.7% | 9.2% | 9.6% |
| Age 75 to 84 | 5.9% | 4.8% | 4.5% |
| Age 85 and over | 3.5% | 2.3% | 1.9% |
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| Race | | | |
| | Tiffin, OH | Dover, NH | United States |
| White | 88.9% | 87.8% | 59.4% |
| Black | 4.2% | 1.0% | 12.2% |
| Asian | 1.1% | 4.4% | 5.6% |
| Native American | 0.3% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.2% | 0.4% |
| Two or More Races | 1.8% | 3.1% | 3.2% |
| Hispanic | 3.6% | 3.4% | 18.4% |
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| Marriage & Family | | | |
| | Tiffin, OH | Dover, NH | United States |
| Married Population | 38.6% | 49.9% | 49.8% |
| Currently Married | 36.8% | 48.5% | 48.0% |
| Married but Separated | 1.8% | 1.5% | 1.8% |
| Single Population | 61.4% | 50.1% | 50.2% |
| Never Married | 42.0% | 36.0% | 33.8% |
| Divorced | 12.4% | 10.4% | 10.8% |
| Widowed | 7.0% | 3.7% | 5.6% |
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| Household Size | 2.17 | 2.16 | 2.60 |
| Households | 7,193 | 14,707 | 124,010,992 |
| Family Households | 3,834 | 8,105 | 80,755,759 |
| Married couple, w/children | 23.1% | 31.2% | 30.5% |
| Married couple, no children | 46.6% | 50.0% | 42.9% |
| Non Family Households | 3,359 | 6,602 | 43,255,233 |
| Single householder, w/children | 22.3% | 9.5% | 15.8% |
| Single householder, no children | 8.0% | 9.2% | 10.8% |