to a statistically significant reduction in rates of food insecurity (Mykerezi and Mills, 2010; Yen et al., 2008).

An additional study estimated the impact of SNAP on food security using an approach for dealing with self-selection into the program that relied on a few strong assumptions and produced upper and lower bounds on the possible effect of the program (Kreider et al., 2012). The study focused on the impact of SNAP on child nutritional health based on data derived from the 2001-2006 NHANES. The analysis included households with children eligible to participate in SNAP; a final weighted sample of 4,418 children was obtained. Socioeconomic and demographic characteristics of the sample were compared with national estimates obtained from the 2003 CPS, December Supplement. The study also accounted for the possibility of error in the measurement of SNAP participation in survey data. Each of the studies of the impact of SNAP on food insecurity noted above relied on survey-based measures of SNAP participation that have been found to be subject to measurement error when compared with more accurate administrative sources of this information (Meyer et al., 2009). Kreider and colleagues (2011) found that both the lower and upper bounds of the estimated impact of SNAP on food insecurity fell below zero, suggesting that the program reduces food insecurity among participants. In one model, the results implied that SNAP reduces the prevalence of food insecurity by at least 8 percentage points, and perhaps by a larger amount. Taken together, the evidence suggests that SNAP benefits can help alleviate food insecurity; however, the evidence is less conclusive among certain subgroups of SNAP participants.

Overall, the evidence on the impact of SNAP participation on food insecurity is moderately strong. While there have been no randomized controlled trials that can shed light on how SNAP affects household food insecurity, the nonexperimental studies examining this question have made serious efforts to account for the possibility of selection bias in the impact estimates. In particular, these studies have used various methods to account for observed and unobserved factors that lead some households to receive SNAP benefits and others to not participate. Although their methods have varied, the studies generally have found consistently that SNAP benefits lead to a reduction in rates of food insecurity among participating households. The available evidence is not clear, however, on whether poor health status and risk for chronic disease are due to or lead to greater risk for food insecurity.

DATA AND ANALYTICAL CHALLENGES TO ASSESSING
THE ADEQUACY OF SNAP ALLOTMENTS

A number of challenges arise in assessing access to a healthy diet. First, nutrition has many dimensions, and no single measure or standard



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