| | Mountain Lakes, NJ | Fair Lawn, NJ | United States |
| Population | 4,464 | 34,820 | 329,725,481 |
| Female Population | 47.7% | 51.8% | 50.5% |
| Male Population | 52.3% | 48.2% | 49.5% |
| Median Age | 43.4 | 40.5 | 38.4 |
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| Population - 2010 | 4,167 | 32,419 | 309,327,143 |
| Population - 2000 | 4,256 | 31,637 | 285,036,114 |
| Population - 1990 | 3,847 | 30,548 | 251,960,433 |
| Pop. 2000 to Now | -1.4% | 3.9% | 15.6% |
| Pop. 1990 to Now | 9.1% | 7.6% | 30.8% |
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| Population Density | 1,690.9 | 6,780.9 | 93.4 |
| Land Area | 2.6 | 5.1 | 3,531,905.4 |
| Water Area | 0.3 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mountain Lakes, NJ | Fair Lawn, NJ | United States |
| Age 0 to 4 | 4.7% | 4.8% | 5.9% |
| Age 5 to 9 | 10.3% | 7.8% | 6.1% |
| Age 10 to 14 | 11.8% | 8.3% | 6.6% |
| Age 15 to 17 | 6.8% | 3.6% | 3.9% |
| Age 18 to 20 | 1.8% | 3.3% | 4.0% |
| Age 21 to 24 | 4.4% | 3.8% | 5.2% |
| Age 25 to 34 | 2.7% | 9.0% | 13.8% |
| Age 35 to 44 | 10.7% | 14.1% | 12.9% |
| Age 45 to 54 | 24.3% | 13.9% | 12.6% |
| Age 55 to 59 | 6.8% | 7.0% | 6.7% |
| Age 60 to 64 | 4.9% | 6.1% | 6.3% |
| Age 65 to 74 | 6.8% | 11.0% | 9.6% |
| Age 75 to 84 | 2.9% | 4.6% | 4.5% |
| Age 85 and over | 1.2% | 2.8% | 1.9% |
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| Race | | | |
| | Mountain Lakes, NJ | Fair Lawn, NJ | United States |
| White | 81.1% | 68.6% | 59.4% |
| Black | 0.0% | 2.1% | 12.2% |
| Asian | 14.9% | 11.9% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.1% | 0.2% |
| Other | 0.0% | 0.3% | 0.4% |
| Two or More Races | 0.3% | 1.8% | 3.2% |
| Hispanic | 3.6% | 15.1% | 18.4% |
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| Marriage & Family | | | |
| | Mountain Lakes, NJ | Fair Lawn, NJ | United States |
| Married Population | 66.6% | 59.4% | 49.8% |
| Currently Married | 65.6% | 58.4% | 48.0% |
| Married but Separated | 0.9% | 1.0% | 1.8% |
| Single Population | 33.4% | 40.6% | 50.2% |
| Never Married | 21.9% | 26.4% | 33.8% |
| Divorced | 6.1% | 8.7% | 10.8% |
| Widowed | 5.4% | 5.5% | 5.6% |
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| Household Size | 3.16 | 2.91 | 2.60 |
| Households | 1,413 | 11,892 | 124,010,992 |
| Family Households | 1,241 | 9,311 | 80,755,759 |
| Married couple, w/children | 56.2% | 38.8% | 30.5% |
| Married couple, no children | 30.4% | 42.1% | 42.9% |
| Non Family Households | 172 | 2,581 | 43,255,233 |
| Single householder, w/children | 6.6% | 9.5% | 15.8% |
| Single householder, no children | 6.8% | 9.6% | 10.8% |