| | Johnstown, OH | Dublin, OH | United States |
| Population | 5,141 | 48,613 | 329,725,481 |
| Female Population | 50.4% | 49.1% | 50.5% |
| Male Population | 49.6% | 51.0% | 49.5% |
| Median Age | 33.2 | 40.5 | 38.4 |
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| Population - 2010 | 4,656 | 41,522 | 309,327,143 |
| Population - 2000 | 3,440 | 31,392 | 285,036,114 |
| Population - 1990 | 3,237 | 16,366 | 251,960,433 |
| Pop. 2000 to Now | 49.0% | 57.3% | 15.6% |
| Pop. 1990 to Now | 58.4% | 201.7% | 30.8% |
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| Population Density | 1,722.3 | 1,976.2 | 93.4 |
| Land Area | 3.0 | 24.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.4 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Johnstown, OH | Dublin, OH | United States |
| Age 0 to 4 | 8.0% | 5.6% | 5.9% |
| Age 5 to 9 | 7.5% | 8.0% | 6.1% |
| Age 10 to 14 | 6.3% | 9.2% | 6.6% |
| Age 15 to 17 | 4.7% | 5.6% | 3.9% |
| Age 18 to 20 | 3.3% | 2.4% | 4.0% |
| Age 21 to 24 | 7.4% | 2.2% | 5.2% |
| Age 25 to 34 | 15.6% | 8.3% | 13.8% |
| Age 35 to 44 | 16.2% | 15.9% | 12.9% |
| Age 45 to 54 | 5.8% | 17.2% | 12.6% |
| Age 55 to 59 | 4.9% | 7.0% | 6.7% |
| Age 60 to 64 | 5.8% | 5.6% | 6.3% |
| Age 65 to 74 | 10.9% | 8.8% | 9.6% |
| Age 75 to 84 | 2.6% | 2.9% | 4.5% |
| Age 85 and over | 1.0% | 1.2% | 1.9% |
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| Race | | | |
| | Johnstown, OH | Dublin, OH | United States |
| White | 94.2% | 70.6% | 59.4% |
| Black | 0.6% | 2.3% | 12.2% |
| Asian | 0.0% | 19.6% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.4% | 0.4% |
| Two or More Races | 1.8% | 3.1% | 3.2% |
| Hispanic | 3.3% | 3.8% | 18.4% |
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| Marriage & Family | | | |
| | Johnstown, OH | Dublin, OH | United States |
| Married Population | 50.5% | 70.4% | 49.8% |
| Currently Married | 50.5% | 69.7% | 48.0% |
| Married but Separated | 0.0% | 0.7% | 1.8% |
| Single Population | 49.5% | 29.6% | 50.2% |
| Never Married | 34.1% | 20.0% | 33.8% |
| Divorced | 12.0% | 6.2% | 10.8% |
| Widowed | 3.4% | 3.4% | 5.6% |
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| Household Size | 2.65 | 2.79 | 2.60 |
| Households | 1,937 | 17,344 | 124,010,992 |
| Family Households | 1,369 | 13,923 | 80,755,759 |
| Married couple, w/children | 36.4% | 48.8% | 30.5% |
| Married couple, no children | 36.5% | 42.1% | 42.9% |
| Non Family Households | 568 | 3,421 | 43,255,233 |
| Single householder, w/children | 15.5% | 7.4% | 15.8% |
| Single householder, no children | 11.6% | 1.7% | 10.8% |