This chapter provides an overview of how SNAP has evolved over the past fifty years and, previewing the findings from the remainder of the volume, discusses the factors that have affected changes in participation over time; the impact of SNAP on poverty, food security, consumption, health, and obesity; and the interplay between SNAP and other public assistance programs. SNAP is highly responsive to macroeconomic pressures as well as policy choices and has become the most effective antipoverty program for nonelderly households. Overall, higher SNAP benefits reduce the risk of food insecurity, SNAP does not appear to contribute to obesity, and limited evidence suggests that SNAP has long-term health benefits. Nonetheless, there remain considerable gaps in the understanding of SNAP's impacts, particularly regarding impacts on nutrition and health. The program differentially serves the most at-risk households, which creates challenges in assessing program impacts.

This chapter describes the socioeconomic and policy climate in recent decades that had bearing on SNAP participation and presents a formal empirical analysis of those determinants along with detailed simulations of the relative contributions of the economy, policy, and demographics to changes in SNAP participation over time. The results suggest that SNAP is operating effectively as an automatic fiscal stabilizer—nearly 50 percent of the increase in participation from 2007 to 2011 was due to the weak economy—but policy reforms expanding access and benefit generosity also affected participation, accounting for nearly 30 percent of the increase after the Great Recession. The changing demographics of the American household are helping restrain growth in SNAP.

This chapter examines the antipoverty effect of SNAP, using survey and administrative data. The analysis shows that SNAP reduced poverty by 16 percent in 2011, after adjusting for underreporting, and produced even greater reductions in the depth and severity of poverty. The program has a particularly strong alleviative effect on poverty among children, who experience significantly higher rates of poverty than the overall population. Recent policies to increase access to SNAP have increased the program's antipoverty efficacy. SNAP significantly improves the welfare of poor families and plays an important role in mitigating the effect of economic downturns on poverty.

This chapter reviews recent theory and empirical evidence regarding the effect of SNAP on food insecurity and replicates the modeling strategies used in the empirical literature. The authors find that recent evidence suggesting an ameliorative effect of SNAP on food insecurity may not be robust to specification choice or data. Most specifications mirror the existing literature in finding a positive association of food insecurity with SNAP participation. Estimates from some specifications that address selection into SNAP participation do show that SNAP reduces food insecurity as do estimates from models that consider the intensity of SNAP participation.

This chapter describes the relationship between SNAP and food spending. It presents the neoclassical framework for analyzing in-kind transfers such as SNAP, which unambiguously predicts an increase in food spending, and follows with an explanation of the SNAP benefit formula. The chapter then presents new evidence from the Consumer Expenditure Survey on food spending patterns among households overall, SNAP households, and other subgroups of interest. Results show that a substantial fraction of SNAP households spend an amount that is above the program's needs standard and that small families are more likely than large families to spend more on food than the needs standard amount. Actual benefit levels are smaller than the needs standards, and most families spend more on food than their predicted benefit allotment. Because of this, the neoclassical model implies that most families treat their benefits like cash.

This chapter assesses the effects of SNAP on health and nutrition. First, differences between SNAP recipients and nonrecipients are summarized. Using the National Health Interview Survey and the National Health and Nutrition Examination Survey (NHANES), it is established that SNAP recipients are in worse health than are nonrecipients, even on outcomes that may predate SNAP use. Using NHANES, it is shown that SNAP-recipient adults eat a less nutritious diet than do nonrecipients, although SNAP recipient children's nutritional outcomes are not different from those of other children. On average, SNAP recipients are worse off, a fact that complicates evaluation of SNAP's effects. The chapter concludes by reviewing the causal literature about the health and nutrition effects of SNAP.

The central goal of SNAP is to alleviate food insecurity. Recently, some have argued that SNAP should also be used to help reduce obesity rates. This chapter begins by showing how, theoretically, the impact of SNAP on obesity is ambiguous. Next, using data from the National Health and Nutrition Examination Survey (NHANES), higher incomes are, in general, associated with lower rates of obesity, implying that that SNAP participation, which increases resources available for food purchases, would lead to reductions in obesity. Consistent with this, the majority of well-done studies find that SNAP participation leads to declines or no change in the probability of obesity for recipients in comparison to eligible nonrecipients. This chapter concludes with cautionary remarks about how some recent proposals to restructure aspects of SNAP to be "antiobesity" are unlikely to have any impact on obesity but would lead to increases in food insecurity.

This chapter examines how SNAP functions as a component of the broader food assistance safety net for school-age children. Variations in SNAP rules across states and over time have important implications for children's access to school meals, because of policy linkages between programs at both institutional and household levels. Using data from the Survey of Income and Program Participation, the chapter reveals considerable variation in the way that children access and package programs, both cross-sectionally and over time. The sequencing of programs is consistent with use of food assistance as part of a managed process for dealing with food needs: Children are far likelier to add programs sequentially than all at once, in ways that are not always consistent with changes in eligibility, and low-income nonparticipants who are food insecure are substantially more likely to begin participating than are their food-secure counterparts.

This chapter presents evidence on the prevalence of participation in other means-tested transfer programs in combination with SNAP. Evidence from the Survey of Income and Program Participation (SIPP) indicates that receipt of benefits from other traditional transfer programs by SNAP families is common, with 76 percent of those families receiving at least one other major benefit of that type in 2008 to 2009, excluding Medicaid. Over the long term, multiple benefit receipt among SNAP families has fallen, a result of declines in the TANF caseload, which have been larger than increases in the SSI, SSDI, and WIC caseloads. The analysis shows that high marginal tax rates generated by multiple program receipt are relevant for only a small portion of the TANF caseload, namely, the portion of the caseload that is nondisabled, nonelderly, and has earnings in the phase-out regions of the programs where marginal tax rates are high.