| | Fairfield township (Essex County), NJ | North Plainfield, NJ | United States |
| Population | 7,751 | 22,635 | 329,725,481 |
| Female Population | 52.6% | 52.6% | 50.5% |
| Male Population | 47.4% | 47.4% | 49.5% |
| Median Age | 48.5 | 36.6 | 38.4 |
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| Population - 2010 | 7,452 | 21,784 | 309,327,143 |
| Population - 2000 | 7,063 | 21,103 | 285,036,114 |
| Population - 1990 | 7,615 | 18,820 | 251,960,433 |
| Pop. 2000 to Now | 5.6% | 0.7% | 15.6% |
| Pop. 1990 to Now | -2.1% | 12.9% | 30.8% |
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| Population Density | 752.8 | 8,063.8 | 93.4 |
| Land Area | 10.3 | 2.8 | 3,531,905.4 |
| Water Area | 0.2 | 0.0 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Fairfield township (Essex County), NJ | North Plainfield, NJ | United States |
| Age 0 to 4 | 7.2% | 7.6% | 5.9% |
| Age 5 to 9 | 6.3% | 6.0% | 6.1% |
| Age 10 to 14 | 5.3% | 6.2% | 6.6% |
| Age 15 to 17 | 2.9% | 3.3% | 3.9% |
| Age 18 to 20 | 1.5% | 3.6% | 4.0% |
| Age 21 to 24 | 2.8% | 5.2% | 5.2% |
| Age 25 to 34 | 5.9% | 15.0% | 13.8% |
| Age 35 to 44 | 13.5% | 14.2% | 12.9% |
| Age 45 to 54 | 14.9% | 12.1% | 12.6% |
| Age 55 to 59 | 4.9% | 8.0% | 6.7% |
| Age 60 to 64 | 7.3% | 7.5% | 6.3% |
| Age 65 to 74 | 13.1% | 7.6% | 9.6% |
| Age 75 to 84 | 10.7% | 2.2% | 4.5% |
| Age 85 and over | 3.7% | 1.3% | 1.9% |
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| Race | | | |
| | Fairfield township (Essex County), NJ | North Plainfield, NJ | United States |
| White | 89.8% | 22.9% | 59.4% |
| Black | 0.0% | 21.1% | 12.2% |
| Asian | 3.0% | 4.3% | 5.6% |
| Native American | 0.0% | 0.1% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 1.2% | 0.4% |
| Two or More Races | 0.0% | 1.0% | 3.2% |
| Hispanic | 7.2% | 49.5% | 18.4% |
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| Marriage & Family | | | |
| | Fairfield township (Essex County), NJ | North Plainfield, NJ | United States |
| Married Population | 62.7% | 46.3% | 49.8% |
| Currently Married | 62.7% | 43.8% | 48.0% |
| Married but Separated | 0.0% | 2.5% | 1.8% |
| Single Population | 37.3% | 53.7% | 50.2% |
| Never Married | 17.7% | 42.8% | 33.8% |
| Divorced | 10.3% | 7.7% | 10.8% |
| Widowed | 9.3% | 3.2% | 5.6% |
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| Household Size | 2.63 | 2.82 | 2.60 |
| Households | 2,946 | 8,004 | 124,010,992 |
| Family Households | 2,256 | 5,599 | 80,755,759 |
| Married couple, w/children | 36.1% | 30.6% | 30.5% |
| Married couple, no children | 48.4% | 32.3% | 42.9% |
| Non Family Households | 690 | 2,405 | 43,255,233 |
| Single householder, w/children | 10.0% | 12.4% | 15.8% |
| Single householder, no children | 5.5% | 24.7% | 10.8% |