From the Executive Summary: "Since the COVID-19 [coronavirus disease 2019] pandemic began, fewer people have been moving into California from other states and more have been leaving. At the end of September 2021, entrances to California were 8% lower than at the end of March 2020. Exits, following a dip in the first half of 2020, stood 12% higher at the end of September 2021 than at the end of March 2020 -- representing a return to a steady pre-pandemic rate of increase of approximately 4% per year since 2016. Net domestic migration, defined as the difference between entrances and exits, went from 40,000 net exits per quarter prior to the pandemic to 80,000 afterward. This brief uses data through the end of September 2021. These trends are present throughout the state. Since the end of March 2020, new entrances to the state have dropped in 40 of 58 California counties, and when Californians move, they are slightly more likely to leave the state than they were before the pandemic began (true for nearly every county). But the Bay Area stands out, for several reasons. Since the end of March 2020, new entrances to Bay Area counties have dropped more quickly than in other parts of the state. Before the pandemic, San Francisco County was the only net receiver of population from other US states. Today, all California counties lose population to domestic migration. In addition, whereas in every other economic region the move rate fell since the pandemic began, Bay Area residents moved (to any destination) at higher levels (up 0.3 percentage points, to 4.2%), driving a 21% increase in Bay Area exits."
California Policy Lab
California Policy Lab: https://www.capolicylab.org/