Minimum wage data are current as of 2021. Union density is defined as the share of workers in the state who are represented by a union, including union members and other workers who are covered by a union contract, based on the variable “union” from EPI extracts of CPS-ORG microdata. Low-union-density states are the 17 states with the lowest average union densities from 2015–2019 (all less than 8%). Medium-union-density states are the 17 states (including D.C.) in the middle of the union-density rankings (with union densities ranging from 8.3% to 13.3%). High-union-density states are the 17 states with the highest average union densities from 2015–2019 (greater than or equal to 13.5%). See Table 1 for more detail about these groupings. We average union density data across 2015 to 2019 for each state to give a more accurate estimate of states’ typical unionization rates over time. We do not include data beyond 2019 in our averages, to avoid any potential distortions related to the 2020–2021 COVID-19 pandemic and ensuing recession.