| | Darien, NY | Olean, NY | United States |
| Population | 3,027 | 13,941 | 329,725,481 |
| Female Population | 46.9% | 50.7% | 50.5% |
| Male Population | 53.1% | 49.3% | 49.5% |
| Median Age | 46.7 | 38.9 | 38.4 |
| space3 | | | |
| Population - 2010 | 3,156 | 14,404 | 309,327,143 |
| Population - 2000 | 3,061 | 15,347 | 285,036,114 |
| Population - 1990 | 2,979 | 16,946 | 251,960,433 |
| Pop. 2000 to Now | -1.8% | -12.9% | 15.6% |
| Pop. 1990 to Now | 0.9% | -21.1% | 30.8% |
| space4 | | | |
| Population Density | 63.9 | 2,362.9 | 93.4 |
| Land Area | 47.4 | 5.9 | 3,531,905.4 |
| Water Area | 0.2 | 0.3 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Darien, NY | Olean, NY | United States |
| Age 0 to 4 | 5.3% | 5.9% | 5.9% |
| Age 5 to 9 | 5.0% | 6.9% | 6.1% |
| Age 10 to 14 | 4.7% | 7.5% | 6.6% |
| Age 15 to 17 | 1.1% | 4.0% | 3.9% |
| Age 18 to 20 | 7.0% | 2.1% | 4.0% |
| Age 21 to 24 | 4.9% | 5.4% | 5.2% |
| Age 25 to 34 | 10.8% | 12.6% | 13.8% |
| Age 35 to 44 | 10.1% | 13.8% | 12.9% |
| Age 45 to 54 | 6.3% | 11.6% | 12.6% |
| Age 55 to 59 | 9.1% | 5.8% | 6.7% |
| Age 60 to 64 | 12.7% | 7.6% | 6.3% |
| Age 65 to 74 | 14.8% | 10.3% | 9.6% |
| Age 75 to 84 | 6.3% | 4.3% | 4.5% |
| Age 85 and over | 1.9% | 2.2% | 1.9% |
| space1 | | | |
| Race | | | |
| | Darien, NY | Olean, NY | United States |
| White | 95.7% | 88.2% | 59.4% |
| Black | 0.0% | 2.3% | 12.2% |
| Asian | 0.0% | 2.2% | 5.6% |
| Native American | 0.0% | 1.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 0.2% | 0.4% |
| Two or More Races | 0.0% | 4.9% | 3.2% |
| Hispanic | 4.3% | 1.3% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Darien, NY | Olean, NY | United States |
| Married Population | 60.5% | 40.9% | 49.8% |
| Currently Married | 58.3% | 37.4% | 48.0% |
| Married but Separated | 2.1% | 3.5% | 1.8% |
| Single Population | 39.5% | 59.1% | 50.2% |
| Never Married | 26.9% | 36.1% | 33.8% |
| Divorced | 5.9% | 14.5% | 10.8% |
| Widowed | 6.8% | 8.4% | 5.6% |
| space5 | | | |
| Household Size | 2.71 | 2.24 | 2.60 |
| Households | 1,118 | 6,115 | 124,010,992 |
| Family Households | 871 | 3,204 | 80,755,759 |
| Married couple, w/children | 23.3% | 32.0% | 30.5% |
| Married couple, no children | 57.9% | 28.8% | 42.9% |
| Non Family Households | 247 | 2,911 | 43,255,233 |
| Single householder, w/children | 2.4% | 23.7% | 15.8% |
| Single householder, no children | 16.4% | 15.5% | 10.8% |