| | Hempstead, NY | San Francisco, CA | United States |
| Population | 791,018 | 865,933 | 329,725,481 |
| Female Population | 51.0% | 48.8% | 50.5% |
| Male Population | 49.0% | 51.2% | 49.5% |
| Median Age | 40.5 | 38.7 | 38.4 |
| space3 | | | |
| Population - 2010 | 760,725 | 805,519 | 309,327,143 |
| Population - 2000 | 755,924 | 776,733 | 285,036,114 |
| Population - 1990 | 725,639 | 723,959 | 251,960,433 |
| Pop. 2000 to Now | 1.1% | 11.6% | 15.6% |
| Pop. 1990 to Now | 5.3% | 19.7% | 30.8% |
| space4 | | | |
| Population Density | 6,670.1 | 18,478.0 | 93.4 |
| Land Area | 118.6 | 46.9 | 3,531,905.4 |
| Water Area | 73.0 | 185.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Hempstead, NY | San Francisco, CA | United States |
| Age 0 to 4 | 5.7% | 4.4% | 5.9% |
| Age 5 to 9 | 5.9% | 3.5% | 6.1% |
| Age 10 to 14 | 6.3% | 3.7% | 6.6% |
| Age 15 to 17 | 4.0% | 2.0% | 3.9% |
| Age 18 to 20 | 3.8% | 2.3% | 4.0% |
| Age 21 to 24 | 5.2% | 4.5% | 5.2% |
| Age 25 to 34 | 12.2% | 22.6% | 13.8% |
| Age 35 to 44 | 12.6% | 16.1% | 12.9% |
| Age 45 to 54 | 13.6% | 13.2% | 12.6% |
| Age 55 to 59 | 7.3% | 6.0% | 6.7% |
| Age 60 to 64 | 6.7% | 5.7% | 6.3% |
| Age 65 to 74 | 9.9% | 9.1% | 9.6% |
| Age 75 to 84 | 4.5% | 4.3% | 4.5% |
| Age 85 and over | 2.4% | 2.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | Hempstead, NY | San Francisco, CA | United States |
| White | 52.4% | 39.2% | 59.4% |
| Black | 16.5% | 4.9% | 12.2% |
| Asian | 6.9% | 34.1% | 5.6% |
| Native American | 0.1% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.3% | 0.2% |
| Other | 0.7% | 0.6% | 0.4% |
| Two or More Races | 2.5% | 5.3% | 3.2% |
| Hispanic | 21.0% | 15.4% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Hempstead, NY | San Francisco, CA | United States |
| Married Population | 52.8% | 41.5% | 49.8% |
| Currently Married | 51.3% | 40.1% | 48.0% |
| Married but Separated | 1.5% | 1.4% | 1.8% |
| Single Population | 47.2% | 58.5% | 50.2% |
| Never Married | 34.5% | 46.0% | 33.8% |
| Divorced | 7.0% | 8.0% | 10.8% |
| Widowed | 5.7% | 4.5% | 5.6% |
| space5 | | | |
| Household Size | 3.14 | 2.34 | 2.60 |
| Households | 248,907 | 361,222 | 124,010,992 |
| Family Households | 194,787 | 170,465 | 80,755,759 |
| Married couple, w/children | 35.3% | 28.8% | 30.5% |
| Married couple, no children | 40.7% | 47.0% | 42.9% |
| Non Family Households | 54,120 | 190,757 | 43,255,233 |
| Single householder, w/children | 10.9% | 10.0% | 15.8% |
| Single householder, no children | 13.1% | 14.2% | 10.8% |