| | Islandia, NY | Sumter, SC | United States |
| Population | 3,541 | 42,920 | 329,725,481 |
| Female Population | 54.0% | 51.2% | 50.5% |
| Male Population | 46.0% | 48.8% | 49.5% |
| Median Age | 38.8 | 32.3 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,333 | 40,564 | 309,327,143 |
| Population - 2000 | 3,057 | 39,643 | 285,036,114 |
| Population - 1990 | 2,769 | 41,943 | 251,960,433 |
| Pop. 2000 to Now | 8.2% | -0.5% | 15.6% |
| Pop. 1990 to Now | 19.5% | -6.0% | 30.8% |
| space4 | | | |
| Population Density | 1,599.4 | 1,317.3 | 93.4 |
| Land Area | 2.2 | 32.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Islandia, NY | Sumter, SC | United States |
| Age 0 to 4 | 5.1% | 8.0% | 5.9% |
| Age 5 to 9 | 5.2% | 7.4% | 6.1% |
| Age 10 to 14 | 5.1% | 7.6% | 6.6% |
| Age 15 to 17 | 3.4% | 4.0% | 3.9% |
| Age 18 to 20 | 1.9% | 4.4% | 4.0% |
| Age 21 to 24 | 5.1% | 6.6% | 5.2% |
| Age 25 to 34 | 19.0% | 14.8% | 13.8% |
| Age 35 to 44 | 12.9% | 10.2% | 12.9% |
| Age 45 to 54 | 13.0% | 10.1% | 12.6% |
| Age 55 to 59 | 8.0% | 5.7% | 6.7% |
| Age 60 to 64 | 5.9% | 5.3% | 6.3% |
| Age 65 to 74 | 10.7% | 8.6% | 9.6% |
| Age 75 to 84 | 2.6% | 4.0% | 4.5% |
| Age 85 and over | 2.3% | 3.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Islandia, NY | Sumter, SC | United States |
| White | 35.1% | 38.9% | 59.4% |
| Black | 6.0% | 48.0% | 12.2% |
| Asian | 10.9% | 2.1% | 5.6% |
| Native American | 0.9% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 3.8% | 0.6% | 0.4% |
| Two or More Races | 4.2% | 2.9% | 3.2% |
| Hispanic | 39.2% | 7.2% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Islandia, NY | Sumter, SC | United States |
| Married Population | 49.6% | 47.5% | 49.8% |
| Currently Married | 43.9% | 43.4% | 48.0% |
| Married but Separated | 5.6% | 4.1% | 1.8% |
| Single Population | 50.4% | 52.5% | 50.2% |
| Never Married | 29.3% | 35.0% | 33.8% |
| Divorced | 13.3% | 10.0% | 10.8% |
| Widowed | 7.8% | 7.5% | 5.6% |
| space5 | | | |
| Household Size | 3.04 | 2.50 | 2.60 |
| Households | 1,151 | 16,595 | 124,010,992 |
| Family Households | 875 | 10,400 | 80,755,759 |
| Married couple, w/children | 26.1% | 24.6% | 30.5% |
| Married couple, no children | 42.3% | 38.4% | 42.9% |
| Non Family Households | 276 | 6,195 | 43,255,233 |
| Single householder, w/children | 12.1% | 23.7% | 15.8% |
| Single householder, no children | 19.5% | 13.3% | 10.8% |