| | Marshfield, MA | Eau Claire, WI | United States |
| Population | 25,793 | 69,030 | 329,725,481 |
| Female Population | 51.1% | 51.5% | 50.5% |
| Male Population | 49.0% | 48.5% | 49.5% |
| Median Age | 46.1 | 32.4 | 38.4 |
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| Population - 2010 | 25,207 | 66,307 | 309,327,143 |
| Population - 2000 | 24,324 | 61,704 | 285,036,114 |
| Population - 1990 | 21,531 | 56,856 | 251,960,433 |
| Pop. 2000 to Now | 7.0% | 12.0% | 15.6% |
| Pop. 1990 to Now | 20.9% | 21.5% | 30.8% |
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| Population Density | 901.2 | 2,115.5 | 93.4 |
| Land Area | 28.6 | 32.6 | 3,531,905.4 |
| Water Area | 3.1 | 2.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Marshfield, MA | Eau Claire, WI | United States |
| Age 0 to 4 | 4.6% | 5.0% | 5.9% |
| Age 5 to 9 | 6.7% | 5.3% | 6.1% |
| Age 10 to 14 | 5.1% | 5.2% | 6.6% |
| Age 15 to 17 | 4.1% | 2.8% | 3.9% |
| Age 18 to 20 | 2.8% | 9.5% | 4.0% |
| Age 21 to 24 | 5.4% | 10.9% | 5.2% |
| Age 25 to 34 | 7.5% | 14.8% | 13.8% |
| Age 35 to 44 | 12.6% | 11.4% | 12.9% |
| Age 45 to 54 | 16.5% | 9.8% | 12.6% |
| Age 55 to 59 | 8.6% | 4.8% | 6.7% |
| Age 60 to 64 | 7.7% | 5.7% | 6.3% |
| Age 65 to 74 | 11.1% | 9.0% | 9.6% |
| Age 75 to 84 | 5.0% | 4.0% | 4.5% |
| Age 85 and over | 2.4% | 1.9% | 1.9% |
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| Race | | | |
| | Marshfield, MA | Eau Claire, WI | United States |
| White | 95.2% | 86.2% | 59.4% |
| Black | 0.5% | 1.3% | 12.2% |
| Asian | 0.7% | 5.7% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.1% | 0.7% | 0.2% |
| Other | 0.1% | 0.0% | 0.4% |
| Two or More Races | 0.8% | 2.8% | 3.2% |
| Hispanic | 2.6% | 3.1% | 18.4% |
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| Marriage & Family | | | |
| | Marshfield, MA | Eau Claire, WI | United States |
| Married Population | 56.8% | 40.4% | 49.8% |
| Currently Married | 56.6% | 39.9% | 48.0% |
| Married but Separated | 0.2% | 0.5% | 1.8% |
| Single Population | 43.2% | 59.6% | 50.2% |
| Never Married | 27.5% | 43.8% | 33.8% |
| Divorced | 10.4% | 11.3% | 10.8% |
| Widowed | 5.3% | 4.4% | 5.6% |
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| Household Size | 2.54 | 2.31 | 2.60 |
| Households | 10,094 | 28,346 | 124,010,992 |
| Family Households | 7,274 | 14,964 | 80,755,759 |
| Married couple, w/children | 32.7% | 30.9% | 30.5% |
| Married couple, no children | 46.4% | 45.0% | 42.9% |
| Non Family Households | 2,820 | 13,382 | 43,255,233 |
| Single householder, w/children | 6.9% | 15.8% | 15.8% |
| Single householder, no children | 14.0% | 8.4% | 10.8% |