There were 4,149 fewer people living in Contra Costa County in 2021 compared to 2020, according to population estimates from the US Census Bureau.
This is less than a one percent fall in Contra Costa County’s population, from 1,165,562 in 2020 to 1,161,413 in 2021.
Contra Costa County had the ninth largest population in California in 2021.
The US Census Bureau found more than 73 percent of counties in the US saw a natural decrease in population in 2021. This is up from a 55.5 percent increase in 2020.
The Midwest suffered the most sustained population decreases, with many counties along the US East Coast and through the Rocky Mountains seeing increases.
The US population continues to grow, though at a slower rate than before.
California Counties By Population Change from 2020 to 2021
| County | 2020 Estimated Population | 2021 Estimated Population | % Change in Population From Year to Year |
|---|---|---|---|
| San Benito County | 64,507 | 66,677 | 3.4% |
| Alpine County | 1,198 | 1,235 | 3.1% |
| Calaveras County | 45,327 | 46,221 | 2% |
| Yuba County | 81,932 | 83,421 | 1.8% |
| Madera County | 156,620 | 159,410 | 1.8% |
| Amador County | 40,541 | 41,259 | 1.8% |
| Sierra County | 3,228 | 3,283 | 1.7% |
| Merced County | 281,726 | 286,461 | 1.7% |
| Placer County | 405,741 | 412,300 | 1.6% |
| Riverside County | 2,422,764 | 2,458,395 | 1.5% |
| Del Norte County | 27,709 | 28,100 | 1.4% |
| Lassen County | 32,719 | 33,159 | 1.3% |
| Nevada County | 102,199 | 103,487 | 1.3% |
| San Joaquin County | 780,517 | 789,410 | 1.1% |
| El Dorado County | 191,114 | 193,221 | 1.1% |
| Lake County | 68,174 | 68,766 | 0.9% |
| Kern County | 909,997 | 917,673 | 0.8% |
| Plumas County | 19,769 | 19,915 | 0.7% |
| Tulare County | 473,736 | 477,054 | 0.7% |
| San Bernardino County | 2,182,740 | 2,194,710 | 0.5% |
| Kings County | 152,627 | 153,443 | 0.5% |
| Tuolumne County | 55,516 | 55,810 | 0.5% |
| Fresno County | 1,008,966 | 1,013,581 | 0.5% |
| Siskiyou County | 43,962 | 44,118 | 0.4% |
| Yolo County | 216,255 | 216,986 | 0.3% |
| San Luis Obispo County | 282,231 | 283,159 | 0.3% |
| Mono County | 13,206 | 13,247 | 0.3% |
| Colusa County | 21,853 | 21,917 | 0.3% |
| Imperial County | 179,489 | 179,851 | 0.2% |
| Sacramento County | 1,586,241 | 1,588,921 | 0.2% |
| Shasta County | 181,893 | 182,139 | 0.1% |
| Mariposa County | 17,124 | 17,147 | 0.1% |
| Stanislaus County | 552,710 | 552,999 | 0.1% |
| Modoc County | 8,658 | 8,661 | 0% |
| Humboldt County | 136,351 | 136,310 | 0% |
| Mendocino County | 91,354 | 91,305 | -0.1% |
| Trinity County | 16,088 | 16,060 | -0.2% |
| Tehama County | 65,615 | 65,498 | -0.2% |
| Monterey County | 438,500 | 437,325 | -0.3% |
| Inyo County | 19,023 | 18,970 | -0.3% |
| Glenn County | 28,893 | 28,805 | -0.3% |
| San Diego County | 3,297,252 | 3,286,069 | -0.3% |
| Solano County | 453,274 | 451,716 | -0.3% |
| Contra Costa County | 1,165,562 | 1,161,413 | -0.4% |
| Santa Barbara County | 448,096 | 446,475 | -0.4% |
| Ventura County | 842,921 | 839,784 | -0.4% |
| Sutter County | 99,480 | 99,063 | -0.4% |
| Sonoma County | 488,345 | 485,887 | -0.5% |
| Orange County | 3,184,101 | 3,167,809 | -0.5% |
| Marin County | 261,776 | 260,206 | -0.6% |
| Butte County | 210,083 | 208,309 | -0.8% |
| Santa Cruz County | 270,353 | 267,792 | -0.9% |
| Napa County | 137,608 | 136,207 | -1% |
| Los Angeles County | 9,989,165 | 9,829,544 | -1.6% |
| Alameda County | 1,679,844 | 1,648,556 | -1.9% |
| Santa Clara County | 1,930,598 | 1,885,508 | -2.3% |
| San Mateo County | 762,453 | 737,888 | -3.2% |
| San Francisco County | 870,014 | 815,201 | -6.3% |
