| | Waterbury, CT | Norwalk, CT | United States |
| Population | 113,783 | 90,821 | 329,725,481 |
| Female Population | 50.9% | 50.2% | 50.5% |
| Male Population | 49.1% | 49.8% | 49.5% |
| Median Age | 37.3 | 40.4 | 38.4 |
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| Population - 2010 | 110,347 | 85,955 | 309,327,143 |
| Population - 2000 | 107,271 | 82,951 | 285,036,114 |
| Population - 1990 | 108,961 | 78,331 | 251,960,433 |
| Pop. 2000 to Now | -0.4% | 6.9% | 15.6% |
| Pop. 1990 to Now | -2.0% | 13.2% | 30.8% |
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| Population Density | 3,989.3 | 3,968.4 | 93.4 |
| Land Area | 28.5 | 22.9 | 3,531,905.4 |
| Water Area | 0.4 | 13.5 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Waterbury, CT | Norwalk, CT | United States |
| Age 0 to 4 | 6.8% | 5.8% | 5.9% |
| Age 5 to 9 | 6.7% | 4.8% | 6.1% |
| Age 10 to 14 | 6.5% | 5.4% | 6.6% |
| Age 15 to 17 | 3.6% | 3.3% | 3.9% |
| Age 18 to 20 | 3.7% | 3.2% | 4.0% |
| Age 21 to 24 | 5.8% | 4.4% | 5.2% |
| Age 25 to 34 | 14.5% | 15.0% | 13.8% |
| Age 35 to 44 | 11.4% | 14.0% | 12.9% |
| Age 45 to 54 | 13.8% | 14.0% | 12.6% |
| Age 55 to 59 | 6.4% | 7.9% | 6.7% |
| Age 60 to 64 | 6.3% | 6.5% | 6.3% |
| Age 65 to 74 | 8.1% | 9.4% | 9.6% |
| Age 75 to 84 | 4.3% | 4.0% | 4.5% |
| Age 85 and over | 2.1% | 2.1% | 1.9% |
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| Race | | | |
| | Waterbury, CT | Norwalk, CT | United States |
| White | 39.3% | 51.2% | 59.4% |
| Black | 17.9% | 11.9% | 12.2% |
| Asian | 2.2% | 5.0% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.7% | 0.4% | 0.4% |
| Two or More Races | 3.1% | 2.5% | 3.2% |
| Hispanic | 36.8% | 28.9% | 18.4% |
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| Marriage & Family | | | |
| | Waterbury, CT | Norwalk, CT | United States |
| Married Population | 37.6% | 51.3% | 49.8% |
| Currently Married | 34.1% | 50.1% | 48.0% |
| Married but Separated | 3.5% | 1.2% | 1.8% |
| Single Population | 62.4% | 48.7% | 50.2% |
| Never Married | 43.0% | 34.3% | 33.8% |
| Divorced | 13.8% | 9.9% | 10.8% |
| Widowed | 5.7% | 4.5% | 5.6% |
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| Household Size | 2.48 | 2.54 | 2.60 |
| Households | 45,114 | 35,569 | 124,010,992 |
| Family Households | 26,791 | 22,631 | 80,755,759 |
| Married couple, w/children | 21.7% | 32.1% | 30.5% |
| Married couple, no children | 31.0% | 43.8% | 42.9% |
| Non Family Households | 18,323 | 12,938 | 43,255,233 |
| Single householder, w/children | 29.6% | 12.7% | 15.8% |
| Single householder, no children | 17.7% | 11.4% | 10.8% |