It’s a project by UCLA School of Health’s World Policy Center. From their site: The selection of data sources for the World Policy Analysis Center was based on

It’s a project by UCLA School of Health’s World Policy Center. From their site: The selection of data sources for the World Policy Analysis Center was based on the approach outlined below. Preference was given to primary sources (e.g. constitutions or laws as specified in country’s legislation). If these were not available we obtained information from secondary sources (e.g. referral to a law or policy in a different text). Secondary sources were reviewed in cases where the information from primary sources was unclear or lacking, or to complement this information (with priority given to sources that were comparable across multiple countries). Documents were reviewed in their original language or as translated into one of the UN’s official languages. If you have better data, I’d love to see it.