WIC PARTICIPATION AND MATERNAL BEHAVIOR: BREASTFEEDING AND WORK LEAVE

I. INTRODUCTION The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) is a federal program that provides nutrition education and food to pregnant and postpartum women, infants, and children with the intention of improving nutritional well-being. Total enrollment in the WIC program has been consistently increasing since its inception, growing to 8.7 million in 2013, with program costs exceeding $6.4 billion. (1) Many studies show that women and children who participate in WIC have better health outcomes than those who do not, and these findings have contributed to widespread support for the program. Many studies also show that women who participate in WIC breastfeed at lower rates and for shorter durations than women who do not participate in WIC. However, selection into the WIC program is not random. (2) If, compared to nonparticipants, mothers who participate in WIC are more motivated in their health status, pay closer attention to their and their children's health, or have access to better health care, then comparing participants to nonparticipants will yield upwardly biased estimates of WIC's effects. However, if participants have more disadvantaged access to health, then this comparison would understate the effect of the program. Researchers have used different approaches to address this selection bias. These approaches include comparing more narrowly defined treatment and comparison groups (Bitler and Currie 2005; Figlio, Hamersma, and Roth 2009; Joyce et al. 2005; Joyce, Racine, and Yunzal-Butler 2008), including mother-specific fixed effects to evaluate changes within each individual (Brien and Swann 2001; Chatterji et al. 2002; Kowaleski-Jones and Duncan 2002), using variation in state rules as instrumental variables (IVs) (Brien and Swann 2001; Chatterji et al. 2002), using propensity score matching to estimate the effect of WIC on breastfeeding (Jiang, Foster, and Gibson-Davis 2010), and comparing variation before and after WIC program introduction (Hoynes, Page, and Stevens 2011). With each of these studies, there remain identification issues. As explained by Ludwig and Miller (2005), a large part of the difficulty in measuring the effects of WIC is the absence of a "clearly exogenous source of identifying variation (i.e., a randomized or natural experiment that drives variation across low-income women in WIC enrollment)." Because WIC is a federal program, there is little geographic variation or variation over time in either eligibility criteria or benefit levels to exploit for causal estimation. There is, however, variation in the price of food provided by WIC. WIC provides program participants with credits to be spent on a list of very specific quantity amounts of food. Given that quantities must be within a range set by federal regulations, the value of the specified amount may vary considerably across states. This study exploits interstate variation in food prices as a source of exogeneity in determining the effect of WIC participation on breastfeeding outcomes and maternal employment. In higher food cost states, the value of a specified quantity is greater than in lower food cost states, and might induce higher WIC participation rates. Using a state-level Cost of Living Index (COLI) for groceries as an IV, we estimate the effects of WIC participation for those whose enrollment appears to be driven by food costs, not unobserved personal characteristics. We find insignificant effects of WIC participation on breastfeeding initiation, breastfeeding duration, and percent of milk feedings that are breast milk at 6, 9, and 12 months. We find that WIC participation decreases time spent exclusively breastfeeding by about 4 weeks, a 48% decline, and WIC extends work leave duration by about 3 weeks, a 23% increase. We also conduct falsification tests to mitigate concerns of spurious correlation. First, we re-estimate WIC participation using the utilities and transportation indices finding no statistically significant relationship between these nonfood-related cost of living items and WIC participation. …