| | Colts Neck, NJ | Mendham borough, NJ | United States |
| Population | 9,975 | 4,976 | 329,725,481 |
| Female Population | 51.8% | 55.1% | 50.5% |
| Male Population | 48.2% | 44.9% | 49.5% |
| Median Age | 48 | 47.7 | 38.4 |
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| Population - 2010 | 10,149 | 4,995 | 309,327,143 |
| Population - 2000 | 12,331 | 5,097 | 285,036,114 |
| Population - 1990 | 8,559 | 4,890 | 251,960,433 |
| Pop. 2000 to Now | -20.2% | -5.1% | 15.6% |
| Pop. 1990 to Now | 15.0% | -1.1% | 30.8% |
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| Population Density | 324.6 | 839.0 | 93.4 |
| Land Area | 30.7 | 5.9 | 3,531,905.4 |
| Water Area | 1.1 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Colts Neck, NJ | Mendham borough, NJ | United States |
| Age 0 to 4 | 3.0% | 4.4% | 5.9% |
| Age 5 to 9 | 7.3% | 6.3% | 6.1% |
| Age 10 to 14 | 9.0% | 6.6% | 6.6% |
| Age 15 to 17 | 4.2% | 6.4% | 3.9% |
| Age 18 to 20 | 4.2% | 2.5% | 4.0% |
| Age 21 to 24 | 5.1% | 4.4% | 5.2% |
| Age 25 to 34 | 4.9% | 6.8% | 13.8% |
| Age 35 to 44 | 8.2% | 9.3% | 12.9% |
| Age 45 to 54 | 18.2% | 18.3% | 12.6% |
| Age 55 to 59 | 9.3% | 7.8% | 6.7% |
| Age 60 to 64 | 9.7% | 6.9% | 6.3% |
| Age 65 to 74 | 12.2% | 10.3% | 9.6% |
| Age 75 to 84 | 3.4% | 5.4% | 4.5% |
| Age 85 and over | 1.1% | 4.6% | 1.9% |
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| Race | | | |
| | Colts Neck, NJ | Mendham borough, NJ | United States |
| White | 86.8% | 87.6% | 59.4% |
| Black | 0.3% | 0.9% | 12.2% |
| Asian | 3.3% | 4.2% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.1% | 0.0% | 0.4% |
| Two or More Races | 3.4% | 4.1% | 3.2% |
| Hispanic | 6.2% | 3.2% | 18.4% |
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| Marriage & Family | | | |
| | Colts Neck, NJ | Mendham borough, NJ | United States |
| Married Population | 68.4% | 63.4% | 49.8% |
| Currently Married | 67.4% | 63.2% | 48.0% |
| Married but Separated | 1.0% | 0.1% | 1.8% |
| Single Population | 31.6% | 36.6% | 50.2% |
| Never Married | 20.8% | 24.0% | 33.8% |
| Divorced | 8.5% | 8.6% | 10.8% |
| Widowed | 2.3% | 4.0% | 5.6% |
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| Household Size | 2.86 | 2.68 | 2.60 |
| Households | 3,469 | 1,753 | 124,010,992 |
| Family Households | 2,888 | 1,405 | 80,755,759 |
| Married couple, w/children | 35.4% | 37.8% | 30.5% |
| Married couple, no children | 55.4% | 51.2% | 42.9% |
| Non Family Households | 581 | 348 | 43,255,233 |
| Single householder, w/children | 5.5% | 6.0% | 15.8% |
| Single householder, no children | 3.7% | 5.0% | 10.8% |