| | San Marino, CA | Westlake, TX | United States |
| Population | 12,620 | 1,374 | 329,725,481 |
| Female Population | 48.6% | 52.5% | 50.5% |
| Male Population | 51.4% | 47.5% | 49.5% |
| Median Age | 45.6 | 45.8 | 38.4 |
| space3 | | | |
| Population - 2010 | 13,102 | 999 | 309,327,143 |
| Population - 2000 | 12,945 | 207 | 285,036,114 |
| Population - 1990 | 12,959 | 185 | 251,960,433 |
| Pop. 2000 to Now | -1.2% | 766.2% | 15.6% |
| Pop. 1990 to Now | -1.3% | 869.2% | 30.8% |
| space4 | | | |
| Population Density | 3,351.9 | 204.8 | 93.4 |
| Land Area | 3.8 | 6.7 | 3,531,905.4 |
| Water Area | 0.0 | 0.2 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | San Marino, CA | Westlake, TX | United States |
| Age 0 to 4 | 5.4% | 5.6% | 5.9% |
| Age 5 to 9 | 5.9% | 4.6% | 6.1% |
| Age 10 to 14 | 5.7% | 16.9% | 6.6% |
| Age 15 to 17 | 5.7% | 4.9% | 3.9% |
| Age 18 to 20 | 2.2% | 2.0% | 4.0% |
| Age 21 to 24 | 2.5% | 2.0% | 5.2% |
| Age 25 to 34 | 10.4% | 1.7% | 13.8% |
| Age 35 to 44 | 10.9% | 10.7% | 12.9% |
| Age 45 to 54 | 15.8% | 25.8% | 12.6% |
| Age 55 to 59 | 7.1% | 10.4% | 6.7% |
| Age 60 to 64 | 8.0% | 8.6% | 6.3% |
| Age 65 to 74 | 12.7% | 4.7% | 9.6% |
| Age 75 to 84 | 4.9% | 1.6% | 4.5% |
| Age 85 and over | 2.8% | 0.5% | 1.9% |
| space1 | | | |
| Race | | | |
| | San Marino, CA | Westlake, TX | United States |
| White | 23.7% | 77.9% | 59.4% |
| Black | 0.3% | 0.0% | 12.2% |
| Asian | 66.5% | 10.1% | 5.6% |
| Native American | 0.0% | 0.9% | 0.6% |
| Hawaiian, Pacific Islander | 0.2% | 0.0% | 0.2% |
| Other | 0.0% | 0.0% | 0.4% |
| Two or More Races | 2.3% | 2.3% | 3.2% |
| Hispanic | 7.0% | 8.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | San Marino, CA | Westlake, TX | United States |
| Married Population | 65.9% | 75.8% | 49.8% |
| Currently Married | 65.8% | 75.8% | 48.0% |
| Married but Separated | 0.1% | 0.0% | 1.8% |
| Single Population | 34.1% | 24.2% | 50.2% |
| Never Married | 25.6% | 15.5% | 33.8% |
| Divorced | 2.9% | 7.3% | 10.8% |
| Widowed | 5.6% | 1.4% | 5.6% |
| space5 | | | |
| Household Size | 3.17 | 3.12 | 2.60 |
| Households | 3,942 | 441 | 124,010,992 |
| Family Households | 3,429 | 392 | 80,755,759 |
| Married couple, w/children | 35.7% | 52.3% | 30.5% |
| Married couple, no children | 49.0% | 44.6% | 42.9% |
| Non Family Households | 513 | 49 | 43,255,233 |
| Single householder, w/children | 4.6% | 3.1% | 15.8% |
| Single householder, no children | 10.6% | 0.0% | 10.8% |