| | Shirley, NY | Mastic Beach, NY | United States |
| Population | 28,059 | 15,333 | 329,725,481 |
| Female Population | 48.2% | 55.6% | 50.5% |
| Male Population | 51.8% | 44.4% | 49.5% |
| Median Age | 39 | 38 | 38.4 |
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| Population - 2010 | 28,070 | 12,869 | 309,327,143 |
| Population - 2000 | 25,395 | 11,543 | 285,036,114 |
| Population - 1990 | 22,936 | 10,293 | 251,960,433 |
| Pop. 2000 to Now | 5.8% | 27.1% | 15.6% |
| Pop. 1990 to Now | 17.1% | 42.6% | 30.8% |
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| Population Density | 2,445.9 | 3,248.5 | 93.4 |
| Land Area | 11.5 | 4.7 | 3,531,905.4 |
| Water Area | 0.4 | 0.3 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Shirley, NY | Mastic Beach, NY | United States |
| Age 0 to 4 | 5.6% | 8.1% | 5.9% |
| Age 5 to 9 | 7.0% | 5.9% | 6.1% |
| Age 10 to 14 | 6.5% | 9.6% | 6.6% |
| Age 15 to 17 | 3.3% | 4.1% | 3.9% |
| Age 18 to 20 | 4.4% | 3.2% | 4.0% |
| Age 21 to 24 | 5.5% | 4.9% | 5.2% |
| Age 25 to 34 | 12.1% | 11.4% | 13.8% |
| Age 35 to 44 | 14.0% | 16.6% | 12.9% |
| Age 45 to 54 | 11.6% | 10.6% | 12.6% |
| Age 55 to 59 | 10.9% | 8.2% | 6.7% |
| Age 60 to 64 | 5.9% | 6.4% | 6.3% |
| Age 65 to 74 | 9.7% | 6.3% | 9.6% |
| Age 75 to 84 | 1.9% | 3.0% | 4.5% |
| Age 85 and over | 1.5% | 1.6% | 1.9% |
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| Race | | | |
| | Shirley, NY | Mastic Beach, NY | United States |
| White | 65.6% | 71.8% | 59.4% |
| Black | 7.3% | 7.3% | 12.2% |
| Asian | 3.4% | 1.2% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.2% | 0.4% |
| Two or More Races | 2.4% | 3.5% | 3.2% |
| Hispanic | 21.2% | 16.1% | 18.4% |
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| Marriage & Family | | | |
| | Shirley, NY | Mastic Beach, NY | United States |
| Married Population | 47.6% | 48.9% | 49.8% |
| Currently Married | 46.0% | 47.9% | 48.0% |
| Married but Separated | 1.6% | 1.0% | 1.8% |
| Single Population | 52.4% | 51.1% | 50.2% |
| Never Married | 36.7% | 36.8% | 33.8% |
| Divorced | 9.8% | 6.5% | 10.8% |
| Widowed | 5.9% | 7.8% | 5.6% |
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| Household Size | 3.40 | 3.12 | 2.60 |
| Households | 8,168 | 4,916 | 124,010,992 |
| Family Households | 6,403 | 3,607 | 80,755,759 |
| Married couple, w/children | 32.7% | 26.0% | 30.5% |
| Married couple, no children | 39.2% | 45.1% | 42.9% |
| Non Family Households | 1,765 | 1,309 | 43,255,233 |
| Single householder, w/children | 14.6% | 19.8% | 15.8% |
| Single householder, no children | 13.5% | 9.2% | 10.8% |