| | Allendale, NJ | Holmdel, NJ | United States |
| Population | 6,820 | 17,317 | 329,725,481 |
| Female Population | 52.2% | 52.7% | 50.5% |
| Male Population | 47.8% | 47.3% | 49.5% |
| Median Age | 43.6 | 48.6 | 38.4 |
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| Population - 2010 | 6,515 | 16,778 | 309,327,143 |
| Population - 2000 | 6,699 | 15,781 | 285,036,114 |
| Population - 1990 | 5,900 | 11,532 | 251,960,433 |
| Pop. 2000 to Now | 0.0% | 5.6% | 15.6% |
| Pop. 1990 to Now | 13.6% | 44.6% | 30.8% |
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| Population Density | 2,202.1 | 967.7 | 93.4 |
| Land Area | 3.1 | 17.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Allendale, NJ | Holmdel, NJ | United States |
| Age 0 to 4 | 6.1% | 3.6% | 5.9% |
| Age 5 to 9 | 8.3% | 6.8% | 6.1% |
| Age 10 to 14 | 8.6% | 6.9% | 6.6% |
| Age 15 to 17 | 8.4% | 5.1% | 3.9% |
| Age 18 to 20 | 1.4% | 2.7% | 4.0% |
| Age 21 to 24 | 2.6% | 4.9% | 5.2% |
| Age 25 to 34 | 4.2% | 6.1% | 13.8% |
| Age 35 to 44 | 11.8% | 9.8% | 12.9% |
| Age 45 to 54 | 21.0% | 15.6% | 12.6% |
| Age 55 to 59 | 7.8% | 9.2% | 6.7% |
| Age 60 to 64 | 6.1% | 8.3% | 6.3% |
| Age 65 to 74 | 7.2% | 10.8% | 9.6% |
| Age 75 to 84 | 2.9% | 6.7% | 4.5% |
| Age 85 and over | 3.4% | 3.8% | 1.9% |
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| Race | | | |
| | Allendale, NJ | Holmdel, NJ | United States |
| White | 75.7% | 71.6% | 59.4% |
| Black | 0.9% | 1.0% | 12.2% |
| Asian | 18.6% | 17.5% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 3.9% | 3.6% | 3.2% |
| Hispanic | 1.0% | 6.2% | 18.4% |
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| Marriage & Family | | | |
| | Allendale, NJ | Holmdel, NJ | United States |
| Married Population | 67.9% | 62.1% | 49.8% |
| Currently Married | 66.7% | 61.9% | 48.0% |
| Married but Separated | 1.1% | 0.2% | 1.8% |
| Single Population | 32.1% | 37.9% | 50.2% |
| Never Married | 22.2% | 23.0% | 33.8% |
| Divorced | 2.6% | 7.5% | 10.8% |
| Widowed | 7.4% | 7.4% | 5.6% |
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| Household Size | 3.05 | 2.72 | 2.60 |
| Households | 2,213 | 6,212 | 124,010,992 |
| Family Households | 1,813 | 4,955 | 80,755,759 |
| Married couple, w/children | 62.4% | 36.9% | 30.5% |
| Married couple, no children | 31.2% | 47.0% | 42.9% |
| Non Family Households | 400 | 1,257 | 43,255,233 |
| Single householder, w/children | 2.2% | 6.2% | 15.8% |
| Single householder, no children | 4.2% | 10.0% | 10.8% |