| | Watchung, NJ | Manalapan, NJ | United States |
| Population | 6,483 | 40,637 | 329,725,481 |
| Female Population | 54.2% | 50.3% | 50.5% |
| Male Population | 45.8% | 49.7% | 49.5% |
| Median Age | 45.3 | 43.8 | 38.4 |
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| Population - 2010 | 6,013 | 39,078 | 309,327,143 |
| Population - 2000 | 5,613 | 33,423 | 285,036,114 |
| Population - 1990 | 5,110 | 26,716 | 251,960,433 |
| Pop. 2000 to Now | 7.0% | 17.4% | 15.6% |
| Pop. 1990 to Now | 17.6% | 46.8% | 30.8% |
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| Population Density | 1,077.6 | 1,327.7 | 93.4 |
| Land Area | 6.0 | 30.6 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Watchung, NJ | Manalapan, NJ | United States |
| Age 0 to 4 | 3.2% | 4.8% | 5.9% |
| Age 5 to 9 | 7.3% | 6.3% | 6.1% |
| Age 10 to 14 | 8.9% | 6.8% | 6.6% |
| Age 15 to 17 | 1.7% | 4.6% | 3.9% |
| Age 18 to 20 | 0.8% | 2.4% | 4.0% |
| Age 21 to 24 | 4.5% | 4.4% | 5.2% |
| Age 25 to 34 | 9.4% | 8.4% | 13.8% |
| Age 35 to 44 | 12.9% | 13.9% | 12.9% |
| Age 45 to 54 | 12.5% | 14.9% | 12.6% |
| Age 55 to 59 | 5.6% | 9.2% | 6.7% |
| Age 60 to 64 | 7.2% | 8.0% | 6.3% |
| Age 65 to 74 | 14.6% | 9.9% | 9.6% |
| Age 75 to 84 | 7.2% | 4.5% | 4.5% |
| Age 85 and over | 4.3% | 1.8% | 1.9% |
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| Race | | | |
| | Watchung, NJ | Manalapan, NJ | United States |
| White | 77.0% | 80.9% | 59.4% |
| Black | 0.1% | 3.1% | 12.2% |
| Asian | 14.0% | 6.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.5% | 0.1% | 0.4% |
| Two or More Races | 2.6% | 1.2% | 3.2% |
| Hispanic | 5.8% | 8.5% | 18.4% |
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| Marriage & Family | | | |
| | Watchung, NJ | Manalapan, NJ | United States |
| Married Population | 56.0% | 64.2% | 49.8% |
| Currently Married | 54.3% | 61.9% | 48.0% |
| Married but Separated | 1.7% | 2.2% | 1.8% |
| Single Population | 44.0% | 35.8% | 50.2% |
| Never Married | 28.5% | 24.5% | 33.8% |
| Divorced | 9.1% | 5.9% | 10.8% |
| Widowed | 6.4% | 5.5% | 5.6% |
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| Household Size | 2.84 | 2.78 | 2.60 |
| Households | 2,234 | 14,572 | 124,010,992 |
| Family Households | 1,653 | 11,023 | 80,755,759 |
| Married couple, w/children | 27.9% | 42.5% | 30.5% |
| Married couple, no children | 54.4% | 47.2% | 42.9% |
| Non Family Households | 581 | 3,549 | 43,255,233 |
| Single householder, w/children | 11.1% | 3.1% | 15.8% |
| Single householder, no children | 6.6% | 7.3% | 10.8% |