| | West Islip, NY | Rancho Palos Verdes, CA | United States |
| Population | 27,557 | 42,316 | 329,725,481 |
| Female Population | 48.9% | 51.4% | 50.5% |
| Male Population | 51.1% | 48.6% | 49.5% |
| Median Age | 40.4 | 49.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 28,692 | 41,685 | 309,327,143 |
| Population - 2000 | 28,907 | 41,145 | 285,036,114 |
| Population - 1990 | 28,419 | 41,659 | 251,960,433 |
| Pop. 2000 to Now | -7.3% | -0.7% | 15.6% |
| Pop. 1990 to Now | -5.7% | -1.9% | 30.8% |
| space4 | | | |
| Population Density | 4,372.1 | 3,141.3 | 93.4 |
| Land Area | 6.3 | 13.5 | 3,531,905.4 |
| Water Area | 0.5 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | West Islip, NY | Rancho Palos Verdes, CA | United States |
| Age 0 to 4 | 6.4% | 4.0% | 5.9% |
| Age 5 to 9 | 5.3% | 5.1% | 6.1% |
| Age 10 to 14 | 5.6% | 7.5% | 6.6% |
| Age 15 to 17 | 3.7% | 4.5% | 3.9% |
| Age 18 to 20 | 3.5% | 3.1% | 4.0% |
| Age 21 to 24 | 6.5% | 3.7% | 5.2% |
| Age 25 to 34 | 12.3% | 5.4% | 13.8% |
| Age 35 to 44 | 12.4% | 9.9% | 12.9% |
| Age 45 to 54 | 15.0% | 14.8% | 12.6% |
| Age 55 to 59 | 8.5% | 9.5% | 6.7% |
| Age 60 to 64 | 6.9% | 6.8% | 6.3% |
| Age 65 to 74 | 8.3% | 13.2% | 9.6% |
| Age 75 to 84 | 4.0% | 7.8% | 4.5% |
| Age 85 and over | 1.5% | 4.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | West Islip, NY | Rancho Palos Verdes, CA | United States |
| White | 86.2% | 49.3% | 59.4% |
| Black | 0.7% | 1.7% | 12.2% |
| Asian | 1.9% | 30.9% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.4% | 0.4% |
| Two or More Races | 1.5% | 7.3% | 3.2% |
| Hispanic | 9.6% | 10.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | West Islip, NY | Rancho Palos Verdes, CA | United States |
| Married Population | 56.9% | 64.8% | 49.8% |
| Currently Married | 55.7% | 63.8% | 48.0% |
| Married but Separated | 1.2% | 1.1% | 1.8% |
| Single Population | 43.1% | 35.2% | 50.2% |
| Never Married | 31.6% | 22.2% | 33.8% |
| Divorced | 6.3% | 6.8% | 10.8% |
| Widowed | 5.2% | 6.1% | 5.6% |
| space5 | | | |
| Household Size | 3.16 | 2.73 | 2.60 |
| Households | 8,607 | 15,359 | 124,010,992 |
| Family Households | 7,024 | 12,242 | 80,755,759 |
| Married couple, w/children | 37.2% | 34.0% | 30.5% |
| Married couple, no children | 46.6% | 52.7% | 42.9% |
| Non Family Households | 1,583 | 3,117 | 43,255,233 |
| Single householder, w/children | 8.8% | 4.2% | 15.8% |
| Single householder, no children | 7.4% | 9.1% | 10.8% |