| | Rochester, WA | Billings, MT | United States |
| Population | 6,065 | 115,689 | 329,725,481 |
| Female Population | 50.4% | 50.4% | 50.5% |
| Male Population | 49.6% | 49.6% | 49.5% |
| Median Age | 40.4 | 37.6 | 38.4 |
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| Population - 2010 | 2,007 | 104,524 | 309,327,143 |
| Population - 2000 | 1,829 | 89,847 | 285,036,114 |
| Population - 1990 | 1,250 | 81,151 | 251,960,433 |
| Pop. 2000 to Now | 75.2% | 22.1% | 15.6% |
| Pop. 1990 to Now | 156.4% | 35.2% | 30.8% |
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| Population Density | 2,603.0 | 2,630.3 | 93.4 |
| Land Area | 2.3 | 44.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Rochester, WA | Billings, MT | United States |
| Age 0 to 4 | 10.6% | 6.2% | 5.9% |
| Age 5 to 9 | 4.3% | 6.3% | 6.1% |
| Age 10 to 14 | 5.6% | 6.7% | 6.6% |
| Age 15 to 17 | 3.2% | 3.8% | 3.9% |
| Age 18 to 20 | 5.6% | 3.3% | 4.0% |
| Age 21 to 24 | 2.2% | 5.4% | 5.2% |
| Age 25 to 34 | 11.9% | 14.7% | 13.8% |
| Age 35 to 44 | 10.7% | 13.2% | 12.9% |
| Age 45 to 54 | 18.6% | 10.6% | 12.6% |
| Age 55 to 59 | 6.0% | 5.7% | 6.7% |
| Age 60 to 64 | 5.3% | 6.7% | 6.3% |
| Age 65 to 74 | 6.0% | 10.0% | 9.6% |
| Age 75 to 84 | 9.7% | 5.0% | 4.5% |
| Age 85 and over | 0.3% | 2.4% | 1.9% |
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| Race | | | |
| | Rochester, WA | Billings, MT | United States |
| White | 76.3% | 83.7% | 59.4% |
| Black | 0.0% | 0.5% | 12.2% |
| Asian | 0.7% | 0.8% | 5.6% |
| Native American | 2.3% | 4.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.6% | 0.2% | 0.4% |
| Two or More Races | 1.6% | 3.6% | 3.2% |
| Hispanic | 17.5% | 6.9% | 18.4% |
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| Marriage & Family | | | |
| | Rochester, WA | Billings, MT | United States |
| Married Population | 55.9% | 48.3% | 49.8% |
| Currently Married | 54.1% | 47.5% | 48.0% |
| Married but Separated | 1.7% | 0.8% | 1.8% |
| Single Population | 44.1% | 51.7% | 50.2% |
| Never Married | 26.7% | 31.3% | 33.8% |
| Divorced | 12.1% | 14.7% | 10.8% |
| Widowed | 5.3% | 5.6% | 5.6% |
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| Household Size | 2.73 | 2.33 | 2.60 |
| Households | 2,221 | 48,478 | 124,010,992 |
| Family Households | 1,536 | 28,249 | 80,755,759 |
| Married couple, w/children | 33.1% | 31.5% | 30.5% |
| Married couple, no children | 46.6% | 43.8% | 42.9% |
| Non Family Households | 685 | 20,229 | 43,255,233 |
| Single householder, w/children | 10.2% | 17.1% | 15.8% |
| Single householder, no children | 10.1% | 7.6% | 10.8% |