Good morning.

(Here’s the sign-up, if you don’t already get California Today by email.)

Demographic statistics about populations can’t explain everything about why our communities are the way they are: What motivates someone to move to a new city, or to start a family or not, differs from one person to the next. But they’re helpful for spotting trends and exploring larger economic forces.

I recently talked with Tina Daley, the head of demographic research for the state’s Department of Finance, about the trends she’s keeping an eye on and what we can learn from them.

She said her office had been looking at migration and housing affordability. One data point that jumped out was which cities had the biggest shares of young people.

Here are the top cities for residents ages 25 to 34, according to 2017 data from the American Community Survey and compiled by Ms. Daley’s team:

1. Mountain View, with 24.4 percent of its 81,443 residents ages 25 to 34.

2. San Francisco, with 23.5 percent of its 884,363 residents