| | Monroe, MI | Erie, PA | United States |
| Population | 20,344 | 95,536 | 329,725,481 |
| Female Population | 53.8% | 50.8% | 50.5% |
| Male Population | 46.2% | 49.2% | 49.5% |
| Median Age | 37.9 | 35.1 | 38.4 |
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| Population - 2010 | 20,543 | 101,719 | 309,327,143 |
| Population - 2000 | 22,076 | 103,717 | 285,036,114 |
| Population - 1990 | 22,902 | 108,718 | 251,960,433 |
| Pop. 2000 to Now | -12.5% | -8.3% | 15.6% |
| Pop. 1990 to Now | -15.6% | -12.6% | 30.8% |
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| Population Density | 2,248.5 | 4,992.0 | 93.4 |
| Land Area | 9.0 | 19.1 | 3,531,905.4 |
| Water Area | 1.2 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Monroe, MI | Erie, PA | United States |
| Age 0 to 4 | 7.9% | 6.4% | 5.9% |
| Age 5 to 9 | 7.3% | 5.8% | 6.1% |
| Age 10 to 14 | 5.9% | 6.2% | 6.6% |
| Age 15 to 17 | 3.0% | 3.9% | 3.9% |
| Age 18 to 20 | 3.0% | 5.5% | 4.0% |
| Age 21 to 24 | 4.2% | 6.6% | 5.2% |
| Age 25 to 34 | 15.5% | 15.5% | 13.8% |
| Age 35 to 44 | 11.7% | 10.9% | 12.9% |
| Age 45 to 54 | 11.7% | 11.3% | 12.6% |
| Age 55 to 59 | 7.4% | 6.4% | 6.7% |
| Age 60 to 64 | 7.2% | 6.6% | 6.3% |
| Age 65 to 74 | 9.0% | 8.9% | 9.6% |
| Age 75 to 84 | 4.0% | 3.9% | 4.5% |
| Age 85 and over | 2.3% | 2.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Monroe, MI | Erie, PA | United States |
| White | 87.0% | 68.0% | 59.4% |
| Black | 5.9% | 15.2% | 12.2% |
| Asian | 0.4% | 2.8% | 5.6% |
| Native American | 0.7% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.6% | 0.4% |
| Two or More Races | 3.2% | 5.0% | 3.2% |
| Hispanic | 2.5% | 8.1% | 18.4% |
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| Marriage & Family | | | |
| | Monroe, MI | Erie, PA | United States |
| Married Population | 43.5% | 35.4% | 49.8% |
| Currently Married | 42.5% | 32.7% | 48.0% |
| Married but Separated | 1.0% | 2.7% | 1.8% |
| Single Population | 56.5% | 64.6% | 50.2% |
| Never Married | 33.0% | 46.3% | 33.8% |
| Divorced | 16.6% | 12.4% | 10.8% |
| Widowed | 6.9% | 5.9% | 5.6% |
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| Household Size | 2.39 | 2.31 | 2.60 |
| Households | 8,323 | 38,992 | 124,010,992 |
| Family Households | 4,809 | 20,395 | 80,755,759 |
| Married couple, w/children | 28.7% | 20.7% | 30.5% |
| Married couple, no children | 37.7% | 36.3% | 42.9% |
| Non Family Households | 3,514 | 18,597 | 43,255,233 |
| Single householder, w/children | 20.9% | 30.4% | 15.8% |
| Single householder, no children | 12.6% | 12.5% | 10.8% |