| | Rosemont, IL | Somerset, NJ | United States |
| Population | 4,027 | 24,827 | 329,725,481 |
| Female Population | 43.8% | 51.0% | 50.5% |
| Male Population | 56.3% | 49.0% | 49.5% |
| Median Age | 40.3 | 40.2 | 38.4 |
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| Population - 2010 | 4,347 | 22,385 | 309,327,143 |
| Population - 2000 | 4,224 | 23,040 | 285,036,114 |
| Population - 1990 | 3,995 | 22,070 | 251,960,433 |
| Pop. 2000 to Now | -1.8% | 7.4% | 15.6% |
| Pop. 1990 to Now | 3.8% | 12.2% | 30.8% |
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| Population Density | 2,247.2 | 3,922.7 | 93.4 |
| Land Area | 1.8 | 6.3 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Rosemont, IL | Somerset, NJ | United States |
| Age 0 to 4 | 5.5% | 5.0% | 5.9% |
| Age 5 to 9 | 5.2% | 4.9% | 6.1% |
| Age 10 to 14 | 4.2% | 6.1% | 6.6% |
| Age 15 to 17 | 5.1% | 3.1% | 3.9% |
| Age 18 to 20 | 6.2% | 3.5% | 4.0% |
| Age 21 to 24 | 3.8% | 5.3% | 5.2% |
| Age 25 to 34 | 16.4% | 13.9% | 13.8% |
| Age 35 to 44 | 11.3% | 14.4% | 12.9% |
| Age 45 to 54 | 15.2% | 14.8% | 12.6% |
| Age 55 to 59 | 8.1% | 5.2% | 6.7% |
| Age 60 to 64 | 7.7% | 7.4% | 6.3% |
| Age 65 to 74 | 6.1% | 9.1% | 9.6% |
| Age 75 to 84 | 3.8% | 4.3% | 4.5% |
| Age 85 and over | 1.4% | 3.0% | 1.9% |
| space1 | | | |
| Race | | | |
| | Rosemont, IL | Somerset, NJ | United States |
| White | 44.3% | 32.3% | 59.4% |
| Black | 0.3% | 32.0% | 12.2% |
| Asian | 4.1% | 21.2% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.1% | 0.4% |
| Two or More Races | 1.8% | 3.3% | 3.2% |
| Hispanic | 49.5% | 11.1% | 18.4% |
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| Marriage & Family | | | |
| | Rosemont, IL | Somerset, NJ | United States |
| Married Population | 49.3% | 48.8% | 49.8% |
| Currently Married | 47.0% | 47.2% | 48.0% |
| Married but Separated | 2.3% | 1.6% | 1.8% |
| Single Population | 50.7% | 51.2% | 50.2% |
| Never Married | 41.8% | 36.5% | 33.8% |
| Divorced | 6.4% | 8.0% | 10.8% |
| Widowed | 2.6% | 6.7% | 5.6% |
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| Household Size | 2.57 | 2.48 | 2.60 |
| Households | 1,567 | 9,838 | 124,010,992 |
| Family Households | 957 | 5,991 | 80,755,759 |
| Married couple, w/children | 31.5% | 35.0% | 30.5% |
| Married couple, no children | 44.0% | 40.5% | 42.9% |
| Non Family Households | 610 | 3,847 | 43,255,233 |
| Single householder, w/children | 18.2% | 12.1% | 15.8% |
| Single householder, no children | 6.4% | 12.5% | 10.8% |