| | Niskayuna, NY | Bethlehem, NY | United States |
| Population | 23,094 | 34,981 | 329,725,481 |
| Female Population | 51.4% | 51.6% | 50.5% |
| Male Population | 48.6% | 48.4% | 49.5% |
| Median Age | 41.9 | 44.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 21,813 | 33,640 | 309,327,143 |
| Population - 2000 | 20,295 | 31,304 | 285,036,114 |
| Population - 1990 | 19,048 | 27,552 | 251,960,433 |
| Pop. 2000 to Now | 10.0% | 11.2% | 15.6% |
| Pop. 1990 to Now | 17.2% | 26.3% | 30.8% |
| space4 | | | |
| Population Density | 1,632.1 | 713.5 | 93.4 |
| Land Area | 14.2 | 49.0 | 3,531,905.4 |
| Water Area | 0.9 | 0.8 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Niskayuna, NY | Bethlehem, NY | United States |
| Age 0 to 4 | 6.3% | 5.4% | 5.9% |
| Age 5 to 9 | 8.5% | 5.1% | 6.1% |
| Age 10 to 14 | 6.8% | 6.7% | 6.6% |
| Age 15 to 17 | 4.5% | 3.9% | 3.9% |
| Age 18 to 20 | 1.7% | 3.7% | 4.0% |
| Age 21 to 24 | 2.4% | 4.2% | 5.2% |
| Age 25 to 34 | 8.9% | 9.9% | 13.8% |
| Age 35 to 44 | 14.7% | 12.2% | 12.9% |
| Age 45 to 54 | 14.4% | 15.5% | 12.6% |
| Age 55 to 59 | 5.7% | 8.1% | 6.7% |
| Age 60 to 64 | 7.6% | 6.6% | 6.3% |
| Age 65 to 74 | 11.1% | 10.1% | 9.6% |
| Age 75 to 84 | 4.9% | 5.4% | 4.5% |
| Age 85 and over | 2.6% | 3.1% | 1.9% |
| space1 | | | |
| Race | | | |
| | Niskayuna, NY | Bethlehem, NY | United States |
| White | 78.3% | 87.5% | 59.4% |
| Black | 3.2% | 2.7% | 12.2% |
| Asian | 11.0% | 4.0% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.5% | 0.2% | 0.4% |
| Two or More Races | 2.9% | 1.7% | 3.2% |
| Hispanic | 4.2% | 3.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Niskayuna, NY | Bethlehem, NY | United States |
| Married Population | 61.5% | 57.7% | 49.8% |
| Currently Married | 59.7% | 57.0% | 48.0% |
| Married but Separated | 1.8% | 0.7% | 1.8% |
| Single Population | 38.5% | 42.3% | 50.2% |
| Never Married | 24.6% | 27.2% | 33.8% |
| Divorced | 9.1% | 8.8% | 10.8% |
| Widowed | 4.9% | 6.2% | 5.6% |
| space5 | | | |
| Household Size | 2.70 | 2.41 | 2.60 |
| Households | 8,413 | 14,328 | 124,010,992 |
| Family Households | 5,900 | 9,428 | 80,755,759 |
| Married couple, w/children | 41.0% | 36.5% | 30.5% |
| Married couple, no children | 46.1% | 49.2% | 42.9% |
| Non Family Households | 2,513 | 4,900 | 43,255,233 |
| Single householder, w/children | 7.5% | 7.7% | 15.8% |
| Single householder, no children | 5.4% | 6.6% | 10.8% |