| | Martha Lake, WA | Monroe, WA | United States |
| Population | 22,251 | 19,879 | 329,725,481 |
| Female Population | 50.2% | 43.6% | 50.5% |
| Male Population | 49.8% | 56.5% | 49.5% |
| Median Age | 34.6 | 34.7 | 38.4 |
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| Population - 2010 | 15,635 | 17,369 | 309,327,143 |
| Population - 2000 | 12,633 | 13,795 | 285,036,114 |
| Population - 1990 | 10,155 | 4,278 | 251,960,433 |
| Pop. 2000 to Now | 58.5% | 49.9% | 15.6% |
| Pop. 1990 to Now | 97.2% | 383.4% | 30.8% |
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| Population Density | 4,842.4 | 3,244.5 | 93.4 |
| Land Area | 4.6 | 6.1 | 3,531,905.4 |
| Water Area | 0.1 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Martha Lake, WA | Monroe, WA | United States |
| Age 0 to 4 | 7.1% | 8.4% | 5.9% |
| Age 5 to 9 | 5.6% | 4.9% | 6.1% |
| Age 10 to 14 | 8.9% | 5.2% | 6.6% |
| Age 15 to 17 | 3.8% | 3.5% | 3.9% |
| Age 18 to 20 | 3.7% | 2.5% | 4.0% |
| Age 21 to 24 | 4.1% | 6.2% | 5.2% |
| Age 25 to 34 | 17.6% | 19.9% | 13.8% |
| Age 35 to 44 | 18.0% | 15.3% | 12.9% |
| Age 45 to 54 | 11.9% | 14.0% | 12.6% |
| Age 55 to 59 | 4.5% | 5.4% | 6.7% |
| Age 60 to 64 | 4.3% | 5.7% | 6.3% |
| Age 65 to 74 | 6.8% | 5.8% | 9.6% |
| Age 75 to 84 | 3.3% | 2.6% | 4.5% |
| Age 85 and over | 0.5% | 0.6% | 1.9% |
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| Race | | | |
| | Martha Lake, WA | Monroe, WA | United States |
| White | 64.5% | 66.4% | 59.4% |
| Black | 3.3% | 4.0% | 12.2% |
| Asian | 18.1% | 3.8% | 5.6% |
| Native American | 0.0% | 0.6% | 0.6% |
| Hawaiian, Pacific Islander | 0.3% | 0.5% | 0.2% |
| Other | 1.5% | 0.6% | 0.4% |
| Two or More Races | 5.2% | 6.8% | 3.2% |
| Hispanic | 7.2% | 17.4% | 18.4% |
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| Marriage & Family | | | |
| | Martha Lake, WA | Monroe, WA | United States |
| Married Population | 58.2% | 48.4% | 49.8% |
| Currently Married | 57.8% | 46.9% | 48.0% |
| Married but Separated | 0.4% | 1.5% | 1.8% |
| Single Population | 41.8% | 51.6% | 50.2% |
| Never Married | 29.9% | 35.7% | 33.8% |
| Divorced | 8.7% | 12.1% | 10.8% |
| Widowed | 3.1% | 3.7% | 5.6% |
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| Household Size | 2.88 | 2.83 | 2.60 |
| Households | 7,697 | 5,833 | 124,010,992 |
| Family Households | 5,562 | 4,363 | 80,755,759 |
| Married couple, w/children | 44.6% | 36.9% | 30.5% |
| Married couple, no children | 37.9% | 39.2% | 42.9% |
| Non Family Households | 2,135 | 1,470 | 43,255,233 |
| Single householder, w/children | 9.5% | 17.5% | 15.8% |
| Single householder, no children | 7.9% | 6.4% | 10.8% |