The biggest drop was in San Francisco, where the rate went from nine homicides per 100,000 people to five per 100,000, according to estimates by the University of Wisconsin Population Health Institute and based on data from the Centers for Disease Control and Prevention.
The rates are based on an average of data from 2002 to 2008 and from 2012 to 2017.
No county showed an increased homicide rate, and three — Marin, Santa Clara and Solano — showed no change.
Here’s how the counties rank by the change in the rate.
1. San Francisco — -4 2. Alameda — -33. Contra Costa — -3 4. San Mateo — -25. Napa — -16. Sonoma — -17. Marin — 08. Santa Clara — 09. Solano — 0Looking at 2019, Solano County has the highest estimated rate, with eight homicides per 100,000 residents, followed by Alameda County at seven and Contra Costa County at six. San Francisco’s estimated homicide rate is five per 100,000 for 2019.
“There is no clear or simple explanation as to why the homicide rates in each county are either steady or declining,” said Lisa Fujie Parks, associate program director for the Prevention Institute.
Parks added that over the last 15 years, the base of knowledge and methods for effective violence prevention have grown significantly.