| | Walnut Creek, CA | Marina del Rey, CA | United States |
| Population | 69,876 | 9,355 | 329,725,481 |
| Female Population | 52.4% | 50.2% | 50.5% |
| Male Population | 47.6% | 49.8% | 49.5% |
| Median Age | 47.8 | 37.1 | 38.4 |
| space3 | | | |
| Population - 2010 | 64,376 | 9,196 | 309,327,143 |
| Population - 2000 | 64,296 | 8,176 | 285,036,114 |
| Population - 1990 | 60,569 | 7,431 | 251,960,433 |
| Pop. 2000 to Now | 8.8% | 17.0% | 15.6% |
| Pop. 1990 to Now | 15.5% | 28.7% | 30.8% |
| space4 | | | |
| Population Density | 3,537.0 | 10,903.3 | 93.4 |
| Land Area | 19.8 | 0.9 | 3,531,905.4 |
| Water Area | 0.0 | 0.6 | 264,836.8 |
| space | | | |
| Est. Total Population By Age | | | |
| | Walnut Creek, CA | Marina del Rey, CA | United States |
| Age 0 to 4 | 4.8% | 8.0% | 5.9% |
| Age 5 to 9 | 4.5% | 1.7% | 6.1% |
| Age 10 to 14 | 3.8% | 1.1% | 6.6% |
| Age 15 to 17 | 2.9% | 0.1% | 3.9% |
| Age 18 to 20 | 2.0% | 1.3% | 4.0% |
| Age 21 to 24 | 3.2% | 9.1% | 5.2% |
| Age 25 to 34 | 13.8% | 18.6% | 13.8% |
| Age 35 to 44 | 12.2% | 27.8% | 12.9% |
| Age 45 to 54 | 10.5% | 15.3% | 12.6% |
| Age 55 to 59 | 6.8% | 7.7% | 6.7% |
| Age 60 to 64 | 5.9% | 1.9% | 6.3% |
| Age 65 to 74 | 14.2% | 3.6% | 9.6% |
| Age 75 to 84 | 9.5% | 2.3% | 4.5% |
| Age 85 and over | 5.8% | 1.3% | 1.9% |
| space1 | | | |
| Race | | | |
| | Walnut Creek, CA | Marina del Rey, CA | United States |
| White | 63.4% | 73.5% | 59.4% |
| Black | 2.3% | 6.7% | 12.2% |
| Asian | 17.7% | 6.5% | 5.6% |
| Native American | 0.1% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.4% | 0.6% | 0.2% |
| Other | 0.1% | 0.0% | 0.4% |
| Two or More Races | 6.0% | 4.9% | 3.2% |
| Hispanic | 10.1% | 7.8% | 18.4% |
| space2 | | | |
| Marriage & Family | | | |
| | Walnut Creek, CA | Marina del Rey, CA | United States |
| Married Population | 55.5% | 47.9% | 49.8% |
| Currently Married | 54.2% | 46.0% | 48.0% |
| Married but Separated | 1.3% | 2.0% | 1.8% |
| Single Population | 44.5% | 52.1% | 50.2% |
| Never Married | 25.6% | 42.5% | 33.8% |
| Divorced | 10.5% | 7.0% | 10.8% |
| Widowed | 8.4% | 2.5% | 5.6% |
| space5 | | | |
| Household Size | 2.15 | 1.80 | 2.60 |
| Households | 32,126 | 5,202 | 124,010,992 |
| Family Households | 18,388 | 1,954 | 80,755,759 |
| Married couple, w/children | 29.4% | 29.0% | 30.5% |
| Married couple, no children | 55.3% | 58.7% | 42.9% |
| Non Family Households | 13,738 | 3,248 | 43,255,233 |
| Single householder, w/children | 7.8% | 9.4% | 15.8% |
| Single householder, no children | 7.5% | 3.0% | 10.8% |