The 2010 Census numbers are in, and they confirm California’s population shift from the coast to inland areas. For the first time, a handful of legislative districts in California are over the one million person mark, as eight State Senate districts cross the seven-figure point. Senators Emmerson (R-37), Runner (R-17), Fuller (R-18), Anderson (R-36), Wolk (D-5), Berryhill (R-14), Vargas (D-40) and Gains (R-1) all represent million-person districts, with Emmerson leading the pack at 1.21 million residents.
The Rose Institute researchers compiled the district by district 2010 population numbers and “deviation from the ideal” for California’s Assembly, State Senate, and Congressional districts (click each link to see Excel 
spreadsheets with the district by district details, or for a spreadsheet of 2010 population by county). The deviation figure shows how far from the average district size each district is in California. Relatively small population districts, with negative deviations, need to add population to reach the federal mandate of “one person, one vote.” Relatively large population districts, with positive deviations, need to give up population to reach the required balance of population among districts.
As a rule, incumbents prefer to give up population and have concerns about adding population. New district residents do not have a history with the incumbent and have never had the opportunity to vote for (or against) the incumbent, so new residents present a “wild card” bloc of voters that threaten an incumbent’s hold on a district. This is true for incumbents of both political parties, especially in a state with carefully crafted districts carefully crafted to protect incumbents of both parties in the 2001 redistricting. Of course the Citizens Redistricting Commission is widely expected to start drawing new lines from a “blank slate,” so even districts currently at or very near the ideal population could see significant changes.
The Rose Institute will have more maps, numbers and analysis as we analyze and process the data, but below are some initial tables and maps.
The following tables show the 10 most-populated Congressional districts and the 10 least-populated Congressional districts.
| Largest Congressional Districts (large to small) | ||
| CD | Incumbent | 2010 Population |
| 45 | Mary Bono Mack | 914,209 |
| 44 | Ken Calvert | 844,756 |
| 25 | Howard “Buck” McKeon | 844,320 |
| 49 | Darrell Issa | 797,428 |
| 41 | Jerry Lewis | 797,133 |
| 22 | Kevin McCarthy | 797,084 |
| 11 | Jerry McNerney | 796,753 |
| 21 | Devin Nunes | 784,176 |
| 3 | Dan Lungren | 783,317 |
| 4 | Tom McClintock | 774,261 |
As noted above, click for the spreadsheet of all Congressional district populations and deviations.
| Smallest Congressional Districts (small to large) | ||
| CD | Incumbent | 2010 Population |
| 31 | Xavier Becerra | 611,336 |
| 47 | Loretta Sanchez | 631,422 |
| 33 | Bass Karen | 637,122 |
| 38 | Grace Napolitano | 641,410 |
| 29 | Adam Schiff | 642,138 |
| 32 | Judy Chu | 642,236 |
| 39 | Linda Sanchez | 643,115 |
| 46 | Dana Rohrabacher | 648,663 |
| 9 | Barbara Lee | 648,766 |
| 37 | Laura Richardson | 648,847 |
Below are maps reflecting the changing demographic makeup of California counties (click for a spreadsheet of population by county).
Note the start contrast between slow-growth coastal areas and the varying levels of higher growth inland in the following map of change in total population by county:
Latino / Hispanic population:
Non-Hispanic, Single-race, Asian-American population:
Non-Hispanic, Single-race, African-American population:
The California State Department of Finance has additional maps available on its website.
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