Solidarity and disparity: Declining labor union density and changing racial and educational mortality inequities in the United States.

Background: Recently, United States life expectancy has stagnated or declined for the poor and working class and risen for the middle and upper classes. Declining labor-union density-the percent of workers who are unionized-has precipitated burgeoning income inequity. We examined whether it has also exacerbated racial and educational mortality inequities.

Methods: From CDC, we obtained state-level all-cause and overdose/suicide mortality overall and by gender, gender-race, and gender-education from 1986-2016. State-level union density and demographic and economic confounders came from the Current Population Survey. State-level policy confounders included the minimum wage, the generosity of Aid to Families with Dependent Children or Temporary Assistance for Needy Families, and the generosity of unemployment insurance. To model the exposure-outcome relationship, we used marginal structural modeling. Using state-level inverse-probability-of-treatment-weighted Poisson models with state and year fixed effects, we estimated 3-year moving average union density's effects on the following year's mortality rates. Then, we tested for gender, gender-race, and gender-education effect-modification. Finally, we estimated how racial and educational all-cause mortality inequities would change if union density increased to 1985 or 1988 levels, respectively.

Results: Overall, a 10% increase in union density was associated with a 17% relative decrease in overdose/suicide mortality (95% confidence interval [CI]: 0.70, 0.98), or 5.7 lives saved per 100 000 person-years (95% CI: -10.7, -0.7). Union density's absolute (lives-saved) effects on overdose/suicide mortality were stronger for men than women, but its relative effects were similar across genders. Union density had little effect on all-cause mortality overall or across subgroups, and modeling suggested union-density increases would not affect mortality inequities.

Conclusions: Declining union density (as operationalized in this study) may not explain all-cause mortality inequities, although increases in union density may reduce overdose/suicide mortality.