Examining the Relationship between Meal Costs and the Redemption of the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) Benefits in Oklahoma: An Instrumental Variables Method

Background: The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) prescribes nutritious food for participants to redeem at no cost. Under-redemption is prevalent but varies across geographies. Little is known about whether differences in food costs influence redemption rates. Objectives: We examined the relationship between meal costs and WIC benefit redemptions among Oklahoma households in 2020. We hypothesized that by constraining household budgets, higher meal costs could be associated with higher WIC benefit redemptions. Methods: We merged WIC household-level benefit redemption data from Oklahoma WIC, including participants’ sociodemographics, redemptions for 16 food categories, and county-level meal-cost data. We analyzed the cross-sectional relationship between meal costs and redemption rates overall and by food category in March-December 2020, controlling for participants’ sociodemographics and the average COVID-19 infection rate in the resident county. Multivariable linear regression was applied. To address statistical endogeneity between meal costs and redemption rates for some food categories, an instrumental variable method was adopted. Results: Food benefits redemption was positively associated with meal costs among WIC households in Oklahoma after accounting for endogeneity. A 10-cent higher meal cost was associated with a 3-percentage-point higher mean redemption rate (P < 0.05), although the relationship varied across food categories. Among benefit categories with a significant association between meal costs and redemption, costs exerted the largest association with redemption of whole-grain bread (Coef. = 0.453, P = 0.014) and the smallest association with redemption of whole milk (Coef. = 0.137, P = 0.044). Conclusions: The findings may help policymakers better estimate the potential operational implications of higher food prices, which can be associated with higher WIC budgets through both increased food costs and higher redemption of WIC food benefits.