| | Neptune, NJ | Detroit, MI | United States |
| Population | 28,083 | 645,658 | 329,725,481 |
| Female Population | 51.4% | 52.5% | 50.5% |
| Male Population | 48.7% | 47.5% | 49.5% |
| Median Age | 46.2 | 35 | 38.4 |
| space3 | | | |
| Population - 2010 | 27,968 | 711,198 | 309,327,143 |
| Population - 2000 | 27,690 | 951,270 | 285,036,114 |
| Population - 1990 | 28,148 | 1,027,974 | 251,960,433 |
| Pop. 2000 to Now | -1.3% | -30.1% | 15.6% |
| Pop. 1990 to Now | -2.9% | -35.3% | 30.8% |
| space4 | | | |
| Population Density | 3,432.3 | 4,654.6 | 93.4 |
| Land Area | 8.2 | 138.7 | 3,531,905.4 |
| Water Area | 0.5 | 4.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Neptune, NJ | Detroit, MI | United States |
| Age 0 to 4 | 4.1% | 7.1% | 5.9% |
| Age 5 to 9 | 5.1% | 6.7% | 6.1% |
| Age 10 to 14 | 3.7% | 7.1% | 6.6% |
| Age 15 to 17 | 2.8% | 4.0% | 3.9% |
| Age 18 to 20 | 4.1% | 4.2% | 4.0% |
| Age 21 to 24 | 5.2% | 5.5% | 5.2% |
| Age 25 to 34 | 12.6% | 15.4% | 13.8% |
| Age 35 to 44 | 11.3% | 11.7% | 12.9% |
| Age 45 to 54 | 13.0% | 11.9% | 12.6% |
| Age 55 to 59 | 9.7% | 6.1% | 6.7% |
| Age 60 to 64 | 9.0% | 6.2% | 6.3% |
| Age 65 to 74 | 11.1% | 8.5% | 9.6% |
| Age 75 to 84 | 5.2% | 3.9% | 4.5% |
| Age 85 and over | 3.2% | 1.7% | 1.9% |
| space1 | | | |
| Race | | | |
| | Neptune, NJ | Detroit, MI | United States |
| White | 48.1% | 10.1% | 59.4% |
| Black | 32.0% | 77.5% | 12.2% |
| Asian | 2.8% | 1.6% | 5.6% |
| Native American | 0.0% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.4% | 0.5% | 0.4% |
| Two or More Races | 3.2% | 2.2% | 3.2% |
| Hispanic | 13.4% | 7.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Neptune, NJ | Detroit, MI | United States |
| Married Population | 45.5% | 25.1% | 49.8% |
| Currently Married | 44.4% | 22.1% | 48.0% |
| Married but Separated | 1.1% | 3.0% | 1.8% |
| Single Population | 54.5% | 74.9% | 50.2% |
| Never Married | 36.5% | 56.0% | 33.8% |
| Divorced | 11.6% | 12.4% | 10.8% |
| Widowed | 6.4% | 6.5% | 5.6% |
| space5 | | | |
| Household Size | 2.42 | 2.53 | 2.60 |
| Households | 11,482 | 250,096 | 124,010,992 |
| Family Households | 6,936 | 129,711 | 80,755,759 |
| Married couple, w/children | 20.6% | 15.7% | 30.5% |
| Married couple, no children | 51.4% | 21.4% | 42.9% |
| Non Family Households | 4,546 | 120,385 | 43,255,233 |
| Single householder, w/children | 12.6% | 37.5% | 15.8% |
| Single householder, no children | 15.4% | 25.3% | 10.8% |