| | Lexington, MA | South Pasadena, CA | United States |
| Population | 34,235 | 26,837 | 329,725,481 |
| Female Population | 51.3% | 49.9% | 50.5% |
| Male Population | 48.7% | 50.1% | 49.5% |
| Median Age | 46.6 | 40.4 | 38.4 |
| space3 | | | |
| Population - 2010 | 31,512 | 25,602 | 309,327,143 |
| Population - 2000 | 30,355 | 24,292 | 285,036,114 |
| Population - 1990 | 28,974 | 23,936 | 251,960,433 |
| Pop. 2000 to Now | 8.7% | 2.9% | 15.6% |
| Pop. 1990 to Now | 13.9% | 4.4% | 30.8% |
| space4 | | | |
| Population Density | 2,083.2 | 7,877.0 | 93.4 |
| Land Area | 16.4 | 3.4 | 3,531,905.4 |
| Water Area | 0.2 | 0.0 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Lexington, MA | South Pasadena, CA | United States |
| Age 0 to 4 | 3.2% | 5.3% | 5.9% |
| Age 5 to 9 | 6.6% | 6.9% | 6.1% |
| Age 10 to 14 | 10.5% | 7.5% | 6.6% |
| Age 15 to 17 | 6.6% | 3.5% | 3.9% |
| Age 18 to 20 | 2.4% | 1.9% | 4.0% |
| Age 21 to 24 | 2.4% | 3.2% | 5.2% |
| Age 25 to 34 | 3.6% | 12.8% | 13.8% |
| Age 35 to 44 | 11.4% | 17.4% | 12.9% |
| Age 45 to 54 | 19.9% | 16.8% | 12.6% |
| Age 55 to 59 | 7.7% | 6.5% | 6.7% |
| Age 60 to 64 | 5.0% | 5.4% | 6.3% |
| Age 65 to 74 | 12.3% | 7.6% | 9.6% |
| Age 75 to 84 | 5.6% | 3.6% | 4.5% |
| Age 85 and over | 3.0% | 1.6% | 1.9% |
| space1 | | | |
| Race | | | |
| | Lexington, MA | South Pasadena, CA | United States |
| White | 60.1% | 38.5% | 59.4% |
| Black | 1.1% | 3.7% | 12.2% |
| Asian | 31.8% | 32.6% | 5.6% |
| Native American | 0.0% | 0.2% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.7% | 0.5% | 0.4% |
| Two or More Races | 4.1% | 5.0% | 3.2% |
| Hispanic | 2.2% | 19.6% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Lexington, MA | South Pasadena, CA | United States |
| Married Population | 68.7% | 54.3% | 49.8% |
| Currently Married | 67.9% | 53.8% | 48.0% |
| Married but Separated | 0.8% | 0.5% | 1.8% |
| Single Population | 31.3% | 45.7% | 50.2% |
| Never Married | 21.3% | 34.8% | 33.8% |
| Divorced | 5.7% | 7.8% | 10.8% |
| Widowed | 4.3% | 3.1% | 5.6% |
| space5 | | | |
| Household Size | 2.75 | 2.58 | 2.60 |
| Households | 12,301 | 10,345 | 124,010,992 |
| Family Households | 9,753 | 6,872 | 80,755,759 |
| Married couple, w/children | 47.9% | 37.7% | 30.5% |
| Married couple, no children | 41.7% | 39.9% | 42.9% |
| Non Family Households | 2,548 | 3,473 | 43,255,233 |
| Single householder, w/children | 7.2% | 12.3% | 15.8% |
| Single householder, no children | 3.2% | 10.1% | 10.8% |