“There’s a significant and persistent union premium, with unionized workers making more money. Additionally, there’s the spillover effects of this. If you have a high unionization rate in your locality, the other employers pay better as well, to remain competitive — a kind of “rising tides lifts all boats” situation. Without unionization, in the South, it depresses wages across the board, and then in turn it depresses wages across the country because there’s always this threat that auto companies could leave Detroit and go south.”
https://www.vox.com/money/2024/4/24/24138640/uaw-union-vote-volkswagen-tennessee