| | Monmouth Junction, NJ | Yardley, PA | United States |
| Population | 9,728 | 2,585 | 329,725,481 |
| Female Population | 50.5% | 49.9% | 50.5% |
| Male Population | 49.5% | 50.1% | 49.5% |
| Median Age | 39.2 | 43.9 | 38.4 |
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| Population - 2010 | 2,772 | 2,443 | 309,327,143 |
| Population - 2000 | 2,721 | 2,498 | 285,036,114 |
| Population - 1990 | 1,570 | 2,288 | 251,960,433 |
| Pop. 2000 to Now | 29.4% | 0.3% | 15.6% |
| Pop. 1990 to Now | 124.3% | 9.5% | 30.8% |
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| Population Density | 6,511.4 | 2,767.7 | 93.4 |
| Land Area | 1.5 | 0.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.1 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Monmouth Junction, NJ | Yardley, PA | United States |
| Age 0 to 4 | 5.5% | 4.1% | 5.9% |
| Age 5 to 9 | 9.5% | 0.9% | 6.1% |
| Age 10 to 14 | 6.1% | 6.0% | 6.6% |
| Age 15 to 17 | 4.3% | 7.9% | 3.9% |
| Age 18 to 20 | 2.6% | 2.6% | 4.0% |
| Age 21 to 24 | 4.7% | 7.1% | 5.2% |
| Age 25 to 34 | 9.8% | 14.0% | 13.8% |
| Age 35 to 44 | 18.9% | 8.9% | 12.9% |
| Age 45 to 54 | 17.3% | 13.3% | 12.6% |
| Age 55 to 59 | 6.5% | 10.2% | 6.7% |
| Age 60 to 64 | 6.8% | 7.6% | 6.3% |
| Age 65 to 74 | 6.8% | 12.1% | 9.6% |
| Age 75 to 84 | 0.9% | 4.2% | 4.5% |
| Age 85 and over | 0.3% | 1.2% | 1.9% |
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| Race | | | |
| | Monmouth Junction, NJ | Yardley, PA | United States |
| White | 27.9% | 93.0% | 59.4% |
| Black | 6.7% | 1.0% | 12.2% |
| Asian | 52.7% | 0.1% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 1.0% | 0.0% | 0.4% |
| Two or More Races | 3.0% | 2.4% | 3.2% |
| Hispanic | 8.6% | 3.5% | 18.4% |
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| Marriage & Family | | | |
| | Monmouth Junction, NJ | Yardley, PA | United States |
| Married Population | 64.8% | 46.0% | 49.8% |
| Currently Married | 64.2% | 44.7% | 48.0% |
| Married but Separated | 0.6% | 1.3% | 1.8% |
| Single Population | 35.2% | 54.0% | 50.2% |
| Never Married | 26.8% | 37.8% | 33.8% |
| Divorced | 6.6% | 10.7% | 10.8% |
| Widowed | 1.8% | 5.5% | 5.6% |
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| Household Size | 2.71 | 2.25 | 2.60 |
| Households | 3,594 | 1,149 | 124,010,992 |
| Family Households | 2,737 | 659 | 80,755,759 |
| Married couple, w/children | 46.4% | 29.9% | 30.5% |
| Married couple, no children | 41.0% | 44.2% | 42.9% |
| Non Family Households | 857 | 490 | 43,255,233 |
| Single householder, w/children | 9.0% | 18.2% | 15.8% |
| Single householder, no children | 3.7% | 7.7% | 10.8% |