This decade, California’s population will grow by 11.5 percent — about 4.3 million people — according to a report the Department of Finance released last month. That would put California’s total population at 41.7 million, higher than the current populations of all but 30 countries in the world. (California’s current population would rank 34th among countries in the world, higher than, for example, Canada.)

The counties the report says will see the largest changes, many over 20 percent, run up California’s valleys, from Kern up through Butte. Only one county’s population, Sierra, will shrink. A few non-valley counties also show high-percentage growth, including Modoc and Mono.

You can find the press release, maps, and county-by-county projections for 2010, 2015, and 2020 by following links here. For the answer to why they call numbers for 2010 “projections,” you will have to look elsewhere.