California Gov. Jerry Brown signed a measure into law on Sunday that mandates all publicly traded companies with headquarters in the state to include at least one woman on their boards of directors by the end of next year.

The details: California is the first state to enact a law of this type. Under the policy, by 2021, companies with at least five directors are required to have two or three women directors, depending on the size of the board. According to Board Governance Research, women held just 15.5% of the board seats of California-based public companies in 2017.