| | Smithfield, RI | Quincy, MA | United States |
| Population | 21,855 | 100,544 | 329,725,481 |
| Female Population | 52.1% | 49.8% | 50.5% |
| Male Population | 47.9% | 50.2% | 49.5% |
| Median Age | 44.5 | 38.3 | 38.4 |
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| Population - 2010 | 21,400 | 92,457 | 309,327,143 |
| Population - 2000 | 20,613 | 88,025 | 285,036,114 |
| Population - 1990 | 19,163 | 84,985 | 251,960,433 |
| Pop. 2000 to Now | 6.0% | 7.3% | 15.6% |
| Pop. 1990 to Now | 14.0% | 11.1% | 30.8% |
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| Population Density | 830.8 | 6,067.8 | 93.4 |
| Land Area | 26.3 | 16.6 | 3,531,905.4 |
| Water Area | 1.5 | 10.3 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Smithfield, RI | Quincy, MA | United States |
| Age 0 to 4 | 2.7% | 5.2% | 5.9% |
| Age 5 to 9 | 3.6% | 3.8% | 6.1% |
| Age 10 to 14 | 5.1% | 3.8% | 6.6% |
| Age 15 to 17 | 4.2% | 2.0% | 3.9% |
| Age 18 to 20 | 13.2% | 2.0% | 4.0% |
| Age 21 to 24 | 4.9% | 5.4% | 5.2% |
| Age 25 to 34 | 9.4% | 21.6% | 13.8% |
| Age 35 to 44 | 7.4% | 15.1% | 12.9% |
| Age 45 to 54 | 14.3% | 11.2% | 12.6% |
| Age 55 to 59 | 6.3% | 6.8% | 6.7% |
| Age 60 to 64 | 6.8% | 6.3% | 6.3% |
| Age 65 to 74 | 11.0% | 9.9% | 9.6% |
| Age 75 to 84 | 8.2% | 4.1% | 4.5% |
| Age 85 and over | 2.9% | 2.8% | 1.9% |
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| Race | | | |
| | Smithfield, RI | Quincy, MA | United States |
| White | 88.5% | 56.7% | 59.4% |
| Black | 1.2% | 5.8% | 12.2% |
| Asian | 3.0% | 29.8% | 5.6% |
| Native American | 0.1% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.1% | 0.5% | 0.4% |
| Two or More Races | 2.0% | 2.4% | 3.2% |
| Hispanic | 5.2% | 4.6% | 18.4% |
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| Marriage & Family | | | |
| | Smithfield, RI | Quincy, MA | United States |
| Married Population | 45.7% | 46.8% | 49.8% |
| Currently Married | 45.3% | 45.1% | 48.0% |
| Married but Separated | 0.4% | 1.7% | 1.8% |
| Single Population | 54.3% | 53.2% | 50.2% |
| Never Married | 39.4% | 40.1% | 33.8% |
| Divorced | 7.6% | 8.4% | 10.8% |
| Widowed | 7.3% | 4.6% | 5.6% |
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| Household Size | 2.35 | 2.23 | 2.60 |
| Households | 7,828 | 44,515 | 124,010,992 |
| Family Households | 4,855 | 23,022 | 80,755,759 |
| Married couple, w/children | 30.7% | 31.0% | 30.5% |
| Married couple, no children | 56.4% | 44.5% | 42.9% |
| Non Family Households | 2,973 | 21,493 | 43,255,233 |
| Single householder, w/children | 7.0% | 11.1% | 15.8% |
| Single householder, no children | 5.9% | 13.4% | 10.8% |