Minimum wage laws are increasingly being recognized as a possible policy lever for improving population health and health equity, with the potential for implementation at the local, state, and national levels. On June 30, 2017, Minneapolis, Minnesota became the 40th local jurisdiction to set the minimum wage above the state level. The city will incrementally increase the minimum wage to $15 an hour by July 1, 2022 for all firms with greater than 100 employees; minimum wage in smaller firms will increase to $13.50 during this time period. The ordinance is expected to increase wages among the 71,000 workers likely to be affected, who are disproportionately non-Hispanic black and Hispanic workers. The available evidence suggests that minimum wage laws may be associated with a range of health outcomes. This includes obesity, as increasing wages can improve food security and reduce cost constraints for purchasing healthier foods. However, existing studies linking wages and weight have design weaknesses that limit causal inference and the ability to identify causal mechanisms. This study, which has a prospective quasi-experimental design with a strong counterfactual condition, is the next step for testing whether and how an increase in minimum wage results in improved obesity-related outcomes among low-wage workers. Throughout the 4.5-year implementation of the Minneapolis minimum wage ordinance, we will follow a cohort of low-wage workers (those earning less than $10 an hour at baseline) in a natural experiment, using a difference-in-difference design to compare a panel of obesity-related measures in a cohort of low-wage workers in Minneapolis (n = 400) and similar workers in a matched control community (n = 400), Raleigh, NC. The control city has a statewide preemption law which prohibits local minimum wage increases. Measures for all individuals will be collected at baseline (T0) and after 5 incremental wage increases (T1-T5) through June 2022. The study aims to test the difference in change in body mass index (BMI, the primary outcome) between individuals in the two conditions, as assessed by anthropometric height-weight measurements. We will also test the difference in change in the two conditions for a range of nutrition-related outcomes, including purchases of healthier and less healthy foods (measured by food purchase receipts), food insecurity (measured by a 6-item USDA measure), and participation in government food assistance programs (measured by participant survey). Finally, we will test other behavioral and psychosocial mechanisms through which wages might affect obesity, and explore spending changes in household health-related expenses over time. Minimum wage laws are a potential upstream approach to prevent obesity, and these policies may be uniquely positioned to reduce health disparities because they intervene on a population (lower-income, high racial/ethnic minority) at the highest risk for poor health. This natural experiment offers a time-sensitive opportunity to test policy effects and contribute a rare health-oriented perspective to the national discourse around the effects of an economic policy.
At present, millions of workers in the United States earn the federal minimum wage of $7.25 or less. Low-income individuals are at an increased risk for obesity and related chronic diseases; raising the minimum wage has the potential to affect obesity by reducing many of its risk factors. In this R01, we will test the effect of an increase in the local minimum wage on changes in obesity-related risk over 5 years.
