| | Sennett, NY | Horseheads, NY | United States |
| Population | 3,335 | 19,326 | 329,725,481 |
| Female Population | 50.1% | 51.9% | 50.5% |
| Male Population | 49.9% | 48.2% | 49.5% |
| Median Age | 47.2 | 45.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,603 | 19,476 | 309,327,143 |
| Population - 2000 | 3,244 | 19,561 | 285,036,114 |
| Population - 1990 | 2,913 | 19,926 | 251,960,433 |
| Pop. 2000 to Now | 3.2% | -4.9% | 15.6% |
| Pop. 1990 to Now | 15.0% | -6.7% | 30.8% |
| space4 | | | |
| Population Density | 115.7 | 542.8 | 93.4 |
| Land Area | 28.8 | 35.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Sennett, NY | Horseheads, NY | United States |
| Age 0 to 4 | 2.5% | 4.9% | 5.9% |
| Age 5 to 9 | 4.3% | 5.6% | 6.1% |
| Age 10 to 14 | 7.7% | 5.8% | 6.6% |
| Age 15 to 17 | 4.4% | 3.5% | 3.9% |
| Age 18 to 20 | 1.9% | 2.8% | 4.0% |
| Age 21 to 24 | 5.4% | 5.7% | 5.2% |
| Age 25 to 34 | 11.5% | 11.2% | 13.8% |
| Age 35 to 44 | 9.3% | 10.4% | 12.9% |
| Age 45 to 54 | 14.3% | 13.2% | 12.6% |
| Age 55 to 59 | 5.7% | 8.6% | 6.7% |
| Age 60 to 64 | 9.3% | 7.5% | 6.3% |
| Age 65 to 74 | 13.5% | 10.0% | 9.6% |
| Age 75 to 84 | 6.8% | 5.0% | 4.5% |
| Age 85 and over | 3.4% | 5.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Sennett, NY | Horseheads, NY | United States |
| White | 91.4% | 85.1% | 59.4% |
| Black | 5.3% | 3.7% | 12.2% |
| Asian | 1.4% | 3.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 0.0% | 5.2% | 3.2% |
| Hispanic | 1.9% | 3.0% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Sennett, NY | Horseheads, NY | United States |
| Married Population | 55.6% | 49.6% | 49.8% |
| Currently Married | 54.9% | 47.8% | 48.0% |
| Married but Separated | 0.6% | 1.8% | 1.8% |
| Single Population | 44.4% | 50.4% | 50.2% |
| Never Married | 29.7% | 31.4% | 33.8% |
| Divorced | 8.7% | 11.0% | 10.8% |
| Widowed | 6.0% | 8.0% | 5.6% |
| space5 | | | |
| Household Size | 2.42 | 2.24 | 2.60 |
| Households | 1,226 | 8,376 | 124,010,992 |
| Family Households | 857 | 4,933 | 80,755,759 |
| Married couple, w/children | 27.8% | 25.2% | 30.5% |
| Married couple, no children | 56.7% | 48.1% | 42.9% |
| Non Family Households | 369 | 3,443 | 43,255,233 |
| Single householder, w/children | 8.3% | 18.8% | 15.8% |
| Single householder, no children | 7.2% | 7.9% | 10.8% |