| | Monroe, CT | Guilford, CT | United States |
| Population | 18,927 | 22,113 | 329,725,481 |
| Female Population | 48.7% | 48.8% | 50.5% |
| Male Population | 51.3% | 51.2% | 49.5% |
| Median Age | 41.4 | 48.9 | 38.4 |
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| Population - 2010 | 19,502 | 22,382 | 309,327,143 |
| Population - 2000 | 19,247 | 21,398 | 285,036,114 |
| Population - 1990 | 16,896 | 19,848 | 251,960,433 |
| Pop. 2000 to Now | 0.4% | 3.0% | 15.6% |
| Pop. 1990 to Now | 14.4% | 11.1% | 30.8% |
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| Population Density | 725.9 | 469.7 | 93.4 |
| Land Area | 26.1 | 47.1 | 3,531,905.4 |
| Water Area | 0.2 | 2.6 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Monroe, CT | Guilford, CT | United States |
| Age 0 to 4 | 7.7% | 5.2% | 5.9% |
| Age 5 to 9 | 4.9% | 5.0% | 6.1% |
| Age 10 to 14 | 8.3% | 6.5% | 6.6% |
| Age 15 to 17 | 4.9% | 4.6% | 3.9% |
| Age 18 to 20 | 2.7% | 2.9% | 4.0% |
| Age 21 to 24 | 5.8% | 3.3% | 5.2% |
| Age 25 to 34 | 7.5% | 6.8% | 13.8% |
| Age 35 to 44 | 12.0% | 11.3% | 12.9% |
| Age 45 to 54 | 15.5% | 13.5% | 12.6% |
| Age 55 to 59 | 9.4% | 7.8% | 6.7% |
| Age 60 to 64 | 6.6% | 8.3% | 6.3% |
| Age 65 to 74 | 8.7% | 14.5% | 9.6% |
| Age 75 to 84 | 4.5% | 7.6% | 4.5% |
| Age 85 and over | 1.7% | 2.7% | 1.9% |
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| Race | | | |
| | Monroe, CT | Guilford, CT | United States |
| White | 78.8% | 86.7% | 59.4% |
| Black | 3.4% | 2.2% | 12.2% |
| Asian | 5.4% | 4.2% | 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 | 3.7% | 1.6% | 3.2% |
| Hispanic | 8.8% | 5.2% | 18.4% |
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| Marriage & Family | | | |
| | Monroe, CT | Guilford, CT | United States |
| Married Population | 62.1% | 62.7% | 49.8% |
| Currently Married | 61.6% | 62.2% | 48.0% |
| Married but Separated | 0.4% | 0.5% | 1.8% |
| Single Population | 37.9% | 37.3% | 50.2% |
| Never Married | 25.2% | 22.9% | 33.8% |
| Divorced | 9.0% | 8.7% | 10.8% |
| Widowed | 3.8% | 5.7% | 5.6% |
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| Household Size | 3.01 | 2.52 | 2.60 |
| Households | 6,274 | 8,665 | 124,010,992 |
| Family Households | 4,956 | 6,254 | 80,755,759 |
| Married couple, w/children | 42.9% | 34.7% | 30.5% |
| Married couple, no children | 45.7% | 53.4% | 42.9% |
| Non Family Households | 1,318 | 2,411 | 43,255,233 |
| Single householder, w/children | 4.1% | 5.5% | 15.8% |
| Single householder, no children | 7.2% | 6.5% | 10.8% |