| | Greenfields, PA | Ontario, CA | United States |
| Population | 1,211 | 175,223 | 329,725,481 |
| Female Population | 49.1% | 50.5% | 50.5% |
| Male Population | 50.9% | 49.5% | 49.5% |
| Median Age | 50 | 32.6 | 38.4 |
| space3 | | | |
| Population - 2010 | 1,053 | 164,380 | 309,327,143 |
| Population - 2000 | 1,072 | 158,007 | 285,036,114 |
| Population - 1990 | 1,163 | 133,179 | 251,960,433 |
| Pop. 2000 to Now | -8.8% | 16.1% | 15.6% |
| Pop. 1990 to Now | -15.9% | 37.7% | 30.8% |
| space4 | | | |
| Population Density | 1,636.5 | 3,507.1 | 93.4 |
| Land Area | 0.7 | 50.0 | 3,531,905.4 |
| Water Area | 0.0 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Greenfields, PA | Ontario, CA | United States |
| Age 0 to 4 | 3.6% | 6.8% | 5.9% |
| Age 5 to 9 | 5.9% | 7.0% | 6.1% |
| Age 10 to 14 | 7.2% | 7.3% | 6.6% |
| Age 15 to 17 | 1.7% | 4.4% | 3.9% |
| Age 18 to 20 | 0.0% | 4.2% | 4.0% |
| Age 21 to 24 | 6.7% | 6.4% | 5.2% |
| Age 25 to 34 | 12.0% | 17.7% | 13.8% |
| Age 35 to 44 | 7.8% | 13.6% | 12.9% |
| Age 45 to 54 | 11.1% | 11.8% | 12.6% |
| Age 55 to 59 | 13.2% | 5.7% | 6.7% |
| Age 60 to 64 | 7.4% | 5.3% | 6.3% |
| Age 65 to 74 | 13.5% | 6.4% | 9.6% |
| Age 75 to 84 | 8.3% | 2.6% | 4.5% |
| Age 85 and over | 1.5% | 0.9% | 1.9% |
| space1 | | | |
| Race | | | |
| | Greenfields, PA | Ontario, CA | United States |
| White | 58.5% | 14.7% | 59.4% |
| Black | 0.0% | 5.2% | 12.2% |
| Asian | 1.7% | 6.8% | 5.6% |
| Native American | 0.0% | 0.3% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.3% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 0.0% | 2.6% | 3.2% |
| Hispanic | 39.7% | 69.9% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Greenfields, PA | Ontario, CA | United States |
| Married Population | 60.2% | 47.0% | 49.8% |
| Currently Married | 59.1% | 44.2% | 48.0% |
| Married but Separated | 1.1% | 2.8% | 1.8% |
| Single Population | 39.8% | 53.0% | 50.2% |
| Never Married | 20.1% | 41.1% | 33.8% |
| Divorced | 14.9% | 8.3% | 10.8% |
| Widowed | 4.9% | 3.7% | 5.6% |
| space5 | | | |
| Household Size | 2.43 | 3.42 | 2.60 |
| Households | 499 | 51,068 | 124,010,992 |
| Family Households | 377 | 40,031 | 80,755,759 |
| Married couple, w/children | 14.3% | 33.8% | 30.5% |
| Married couple, no children | 58.1% | 30.9% | 42.9% |
| Non Family Households | 122 | 11,037 | 43,255,233 |
| Single householder, w/children | 19.9% | 20.2% | 15.8% |
| Single householder, no children | 7.7% | 15.1% | 10.8% |