| | Wauwatosa, WI | Eureka, CA | United States |
| Population | 48,072 | 26,763 | 329,725,481 |
| Female Population | 52.6% | 50.6% | 50.5% |
| Male Population | 47.4% | 49.5% | 49.5% |
| Median Age | 38.4 | 38.2 | 38.4 |
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| Population - 2010 | 46,436 | 27,201 | 309,327,143 |
| Population - 2000 | 47,271 | 26,128 | 285,036,114 |
| Population - 1990 | 49,366 | 27,025 | 251,960,433 |
| Pop. 2000 to Now | 1.7% | 2.0% | 15.6% |
| Pop. 1990 to Now | -2.6% | -1.4% | 30.8% |
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| Population Density | 3,634.4 | 2,852.0 | 93.4 |
| Land Area | 13.2 | 9.4 | 3,531,905.4 |
| Water Area | 0.0 | 5.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Wauwatosa, WI | Eureka, CA | United States |
| Age 0 to 4 | 6.1% | 4.9% | 5.9% |
| Age 5 to 9 | 6.4% | 5.7% | 6.1% |
| Age 10 to 14 | 5.6% | 5.2% | 6.6% |
| Age 15 to 17 | 4.1% | 2.6% | 3.9% |
| Age 18 to 20 | 2.4% | 3.8% | 4.0% |
| Age 21 to 24 | 3.3% | 5.3% | 5.2% |
| Age 25 to 34 | 16.8% | 16.2% | 13.8% |
| Age 35 to 44 | 14.1% | 15.2% | 12.9% |
| Age 45 to 54 | 12.3% | 12.9% | 12.6% |
| Age 55 to 59 | 6.1% | 5.9% | 6.7% |
| Age 60 to 64 | 5.6% | 6.7% | 6.3% |
| Age 65 to 74 | 9.4% | 10.1% | 9.6% |
| Age 75 to 84 | 4.1% | 4.0% | 4.5% |
| Age 85 and over | 3.7% | 1.4% | 1.9% |
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| Race | | | |
| | Wauwatosa, WI | Eureka, CA | United States |
| White | 80.5% | 65.0% | 59.4% |
| Black | 7.0% | 2.4% | 12.2% |
| Asian | 4.5% | 5.7% | 5.6% |
| Native American | 0.4% | 1.7% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.2% | 0.2% |
| Other | 0.2% | 0.3% | 0.4% |
| Two or More Races | 3.9% | 8.3% | 3.2% |
| Hispanic | 3.4% | 16.4% | 18.4% |
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| Marriage & Family | | | |
| | Wauwatosa, WI | Eureka, CA | United States |
| Married Population | 51.3% | 36.1% | 49.8% |
| Currently Married | 49.9% | 34.3% | 48.0% |
| Married but Separated | 1.4% | 1.8% | 1.8% |
| Single Population | 48.7% | 63.9% | 50.2% |
| Never Married | 33.3% | 41.8% | 33.8% |
| Divorced | 9.8% | 17.4% | 10.8% |
| Widowed | 5.6% | 4.8% | 5.6% |
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| Household Size | 2.27 | 2.37 | 2.60 |
| Households | 20,895 | 10,808 | 124,010,992 |
| Family Households | 12,205 | 5,213 | 80,755,759 |
| Married couple, w/children | 35.5% | 27.6% | 30.5% |
| Married couple, no children | 42.9% | 39.2% | 42.9% |
| Non Family Households | 8,690 | 5,595 | 43,255,233 |
| Single householder, w/children | 14.3% | 19.6% | 15.8% |
| Single householder, no children | 7.3% | 13.6% | 10.8% |