| | Johnston, RI | Wallace, ID | United States |
| Population | 29,550 | 1,062 | 329,725,481 |
| Female Population | 51.6% | 45.0% | 50.5% |
| Male Population | 48.4% | 55.0% | 49.5% |
| Median Age | 45.1 | 42.2 | 38.4 |
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| Population - 2010 | 28,877 | 786 | 309,327,143 |
| Population - 2000 | 28,195 | 960 | 285,036,114 |
| Population - 1990 | 26,542 | 1,010 | 251,960,433 |
| Pop. 2000 to Now | 4.2% | -19.0% | 15.6% |
| Pop. 1990 to Now | 10.6% | -23.0% | 30.8% |
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| Population Density | 1,261.2 | 1,169.6 | 93.4 |
| Land Area | 23.4 | 0.9 | 3,531,905.4 |
| Water Area | 0.9 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Johnston, RI | Wallace, ID | United States |
| Age 0 to 4 | 4.5% | 5.3% | 5.9% |
| Age 5 to 9 | 5.6% | 4.7% | 6.1% |
| Age 10 to 14 | 5.1% | 7.4% | 6.6% |
| Age 15 to 17 | 2.9% | 2.2% | 3.9% |
| Age 18 to 20 | 2.6% | 2.4% | 4.0% |
| Age 21 to 24 | 3.3% | 4.2% | 5.2% |
| Age 25 to 34 | 13.3% | 10.2% | 13.8% |
| Age 35 to 44 | 12.6% | 19.3% | 12.9% |
| Age 45 to 54 | 14.5% | 10.6% | 12.6% |
| Age 55 to 59 | 5.3% | 7.3% | 6.7% |
| Age 60 to 64 | 8.8% | 8.3% | 6.3% |
| Age 65 to 74 | 11.4% | 13.8% | 9.6% |
| Age 75 to 84 | 6.6% | 2.5% | 4.5% |
| Age 85 and over | 3.4% | 1.7% | 1.9% |
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| Race | | | |
| | Johnston, RI | Wallace, ID | United States |
| White | 80.0% | 93.3% | 59.4% |
| Black | 4.6% | 0.2% | 12.2% |
| Asian | 1.1% | 0.4% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.3% | 0.0% | 0.4% |
| Two or More Races | 0.8% | 2.4% | 3.2% |
| Hispanic | 13.3% | 3.7% | 18.4% |
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| Marriage & Family | | | |
| | Johnston, RI | Wallace, ID | United States |
| Married Population | 45.5% | 44.7% | 49.8% |
| Currently Married | 44.8% | 40.6% | 48.0% |
| Married but Separated | 0.8% | 4.1% | 1.8% |
| Single Population | 54.5% | 55.3% | 50.2% |
| Never Married | 34.2% | 30.6% | 33.8% |
| Divorced | 11.0% | 19.6% | 10.8% |
| Widowed | 9.2% | 5.1% | 5.6% |
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| Household Size | 2.53 | 2.25 | 2.60 |
| Households | 11,482 | 456 | 124,010,992 |
| Family Households | 7,350 | 236 | 80,755,759 |
| Married couple, w/children | 29.2% | 19.5% | 30.5% |
| Married couple, no children | 40.3% | 47.0% | 42.9% |
| Non Family Households | 4,132 | 220 | 43,255,233 |
| Single householder, w/children | 14.0% | 25.8% | 15.8% |
| Single householder, no children | 16.5% | 7.6% | 10.8% |