| | Westbury, NY | Farmingville, NY | United States |
| Population | 15,772 | 16,909 | 329,725,481 |
| Female Population | 51.5% | 47.4% | 50.5% |
| Male Population | 48.5% | 52.6% | 49.5% |
| Median Age | 42.8 | 35 | 38.4 |
| space3 | | | |
| Population - 2010 | 15,067 | 16,016 | 309,327,143 |
| Population - 2000 | 14,263 | 16,458 | 285,036,114 |
| Population - 1990 | 13,060 | 14,842 | 251,960,433 |
| Pop. 2000 to Now | 7.2% | -8.4% | 15.6% |
| Pop. 1990 to Now | 17.1% | 1.5% | 30.8% |
| space4 | | | |
| Population Density | 6,728.7 | 4,103.1 | 93.4 |
| Land Area | 2.3 | 4.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Westbury, NY | Farmingville, NY | United States |
| Age 0 to 4 | 6.1% | 6.5% | 5.9% |
| Age 5 to 9 | 4.1% | 4.4% | 6.1% |
| Age 10 to 14 | 5.6% | 5.5% | 6.6% |
| Age 15 to 17 | 3.3% | 4.8% | 3.9% |
| Age 18 to 20 | 2.6% | 4.0% | 4.0% |
| Age 21 to 24 | 4.5% | 6.7% | 5.2% |
| Age 25 to 34 | 13.2% | 18.0% | 13.8% |
| Age 35 to 44 | 13.5% | 10.1% | 12.9% |
| Age 45 to 54 | 13.7% | 14.4% | 12.6% |
| Age 55 to 59 | 7.7% | 6.3% | 6.7% |
| Age 60 to 64 | 7.7% | 7.7% | 6.3% |
| Age 65 to 74 | 9.9% | 6.7% | 9.6% |
| Age 75 to 84 | 5.6% | 2.9% | 4.5% |
| Age 85 and over | 2.3% | 1.8% | 1.9% |
| space1 | | | |
| Race | | | |
| | Westbury, NY | Farmingville, NY | United States |
| White | 40.0% | 70.3% | 59.4% |
| Black | 18.9% | 6.1% | 12.2% |
| Asian | 8.6% | 4.4% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.6% | 1.2% | 0.4% |
| Two or More Races | 2.5% | 4.1% | 3.2% |
| Hispanic | 29.4% | 13.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Westbury, NY | Farmingville, NY | United States |
| Married Population | 53.3% | 50.4% | 49.8% |
| Currently Married | 52.6% | 49.3% | 48.0% |
| Married but Separated | 0.7% | 1.1% | 1.8% |
| Single Population | 46.7% | 49.6% | 50.2% |
| Never Married | 35.2% | 39.9% | 33.8% |
| Divorced | 6.0% | 5.6% | 10.8% |
| Widowed | 5.5% | 4.1% | 5.6% |
| space5 | | | |
| Household Size | 2.98 | 3.52 | 2.60 |
| Households | 5,259 | 4,744 | 124,010,992 |
| Family Households | 3,825 | 4,105 | 80,755,759 |
| Married couple, w/children | 30.6% | 33.9% | 30.5% |
| Married couple, no children | 46.9% | 41.3% | 42.9% |
| Non Family Households | 1,434 | 639 | 43,255,233 |
| Single householder, w/children | 10.6% | 10.3% | 15.8% |
| Single householder, no children | 11.9% | 14.5% | 10.8% |