| | Smithfield, NY | Clay, NY | United States |
| Population | 1,314 | 60,464 | 329,725,481 |
| Female Population | 44.4% | 50.8% | 50.5% |
| Male Population | 55.6% | 49.2% | 49.5% |
| Median Age | 41.2 | 39.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,302 | 58,439 | 309,327,143 |
| Population - 2000 | 1,205 | 58,805 | 285,036,114 |
| Population - 1990 | 1,053 | 59,749 | 251,960,433 |
| Pop. 2000 to Now | 3.7% | 0.5% | 15.6% |
| Pop. 1990 to Now | 18.6% | -1.1% | 30.8% |
| space4 | | | |
| Population Density | 53.8 | 1,260.8 | 93.4 |
| Land Area | 24.4 | 48.0 | 3,531,905.4 |
| Water Area | 0.1 | 0.9 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Smithfield, NY | Clay, NY | United States |
| Age 0 to 4 | 4.9% | 4.7% | 5.9% |
| Age 5 to 9 | 5.9% | 6.5% | 6.1% |
| Age 10 to 14 | 8.1% | 5.4% | 6.6% |
| Age 15 to 17 | 3.0% | 3.9% | 3.9% |
| Age 18 to 20 | 0.8% | 2.0% | 4.0% |
| Age 21 to 24 | 3.3% | 5.3% | 5.2% |
| Age 25 to 34 | 15.2% | 14.5% | 13.8% |
| Age 35 to 44 | 13.3% | 14.1% | 12.9% |
| Age 45 to 54 | 11.0% | 13.1% | 12.6% |
| Age 55 to 59 | 7.8% | 7.2% | 6.7% |
| Age 60 to 64 | 10.6% | 6.9% | 6.3% |
| Age 65 to 74 | 9.1% | 10.7% | 9.6% |
| Age 75 to 84 | 4.6% | 4.2% | 4.5% |
| Age 85 and over | 2.4% | 1.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Smithfield, NY | Clay, NY | United States |
| White | 90.3% | 85.2% | 59.4% |
| Black | 1.7% | 3.5% | 12.2% |
| Asian | 0.5% | 2.2% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 7.5% | 4.0% | 3.2% |
| Hispanic | 0.0% | 4.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Smithfield, NY | Clay, NY | United States |
| Married Population | 59.5% | 51.8% | 49.8% |
| Currently Married | 59.1% | 49.7% | 48.0% |
| Married but Separated | 0.4% | 2.2% | 1.8% |
| Single Population | 40.5% | 48.2% | 50.2% |
| Never Married | 26.2% | 32.7% | 33.8% |
| Divorced | 8.2% | 10.4% | 10.8% |
| Widowed | 6.1% | 5.0% | 5.6% |
| space5 | | | |
| Household Size | 3.27 | 2.44 | 2.60 |
| Households | 402 | 24,763 | 124,010,992 |
| Family Households | 322 | 15,681 | 80,755,759 |
| Married couple, w/children | 28.3% | 28.9% | 30.5% |
| Married couple, no children | 58.1% | 48.6% | 42.9% |
| Non Family Households | 80 | 9,082 | 43,255,233 |
| Single householder, w/children | 6.2% | 13.6% | 15.8% |
| Single householder, no children | 7.5% | 8.9% | 10.8% |