United States 

Department of 

Agriculture

Economic

Research

Service

Economic

Research

Report

Number 132

April 2012

Alleviating Poverty 

in the United States:

The Critical Role of SNAP Benefits

Laura Tiehen

Dean Jolliffe

Craig Gundersen
www.ers.usda.gov

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Recommended citation format for this publication:

Tiehen, Laura, Dean Jolliffe, and Craig Gundersen. Alleviating Poverty in 

the United States: The Critical Role of SNAP Benefits, ERR-132, U.S. 

Department of Agriculture, Economic Research Service, April 2012.
United States

Department

of Agriculture

www.ers.usda.gov

A Report from the Economic Research Service

Abstract

The Supplemental Nutrition Assistance Program (SNAP) is one of the largest safety 

net programs in the United States, serving 44.7 million individuals in an average month 

in 2011. We used Current Population Survey data to examine the effect of SNAP on 

poverty from 2000 to 2009, by adding program benefits to income and calculating how 

SNAP benefits affected the prevalence, depth, and severity of poverty. We found an 

average decline of 4.4 percent in the prevalence of poverty due to SNAP benefits, while 

the average decline in the depth and severity of poverty was 10.3 and 13.2 percent, 

respectively. SNAP benefits had a particularly strong effect on child poverty, reducing its 

depth by an average of 15.5 percent and its severity by an average of 21.3 percent from 

2000 to 2009. SNAP’s antipoverty effect peaked in 2009, when benefit increases were 

authorized by the American Recovery and Reinvestment Act. Our analysis shows that 

SNAP significantly improves the welfare of low-income households.

Keywords: SNAP, food stamps, food assistance, poverty, child poverty, nonmetropolitan 

poverty, Current Population Survey

Acknowledgments

The authors thank Christopher R. Bollinger, University of Kentucky; Benjamin Cowan, 

Washington State University; Steven Carlson, USDA, Food and Nutrition Service; and 

Economic Research Service colleagues Ephraim Leibtag, David Smallwood, Jessica 

Todd, and Michele Ver Ploeg for helpful reviews of this report. We thank participants at 

the 2011 National Association for Welfare Research and Statistics conference for helpful 

comments. Thanks also to our editor, Priscilla Smith, and our designer Cynthia A. Ray.

About the Authors

Tiehen is a research economist in the USDA, Economic Research Service, Food 

Economics Division. Jolliffe is a senior economist at the World Bank, and Gundersen is 

a professor in the Department of Agricultural and Consumer Economics at the University 

of Illinois.

Laura Tiehen

Dean Jolliffe

Craig Gundersen

Alleviating Poverty in the United States: 

The Critical Role of SNAP Benefits Economic

Research

Report

Number 132 

April 2012
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Contents

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

SNAP: Eligibility, Participation, and Benefits . . . . . . . . . . . . . . . . . . . . . 2

The Current Population Survey Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Measures of Poverty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

The Effect of SNAP Benefits on Poverty . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Appendix Table 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
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Summary

What Is the Issue?

The Supplemental Nutrition Assistance Program (SNAP, formerly called 

the Food Stamp Program) plays a vital role in the social safety net in the 

United States, providing almost $72 billion in benefits in 2011. An important measure of SNAP’s effectiveness is the extent to which the program 

reduces poverty. Evaluations of the antipoverty effect of safety net programs 

often focus on the rate of poverty. However, the poverty rate reflects only 

one aspect of the antipoverty effect of a safety net program—whether or not 

adding program benefits to a family’s resources lifts them above the poverty 

threshold. Two other measures, portraying the depth and severity of poverty, 

capture how program benefits increase income among the poor even if they 

do not lift them out of poverty. Both measures provide richer information 

on how program benefits improve the well-being of poor families, and the 

severity measure is particularly sensitive to how program benefits increase 

well-being among the poorest of the poor.

In this report, we calculated the rate, depth, and severity of poverty, using 

the definition of family income in the official U.S. poverty estimation (which 

does not include SNAP benefits). We then estimated the reduction in the 

three poverty measures for the years 2000 through 2009, after including 

SNAP benefits in family income. Our analysis focuses on a time period that 

includes the 2001 and the 2007-2009 recessions as well as the implementation of additional SNAP benefits through the 2009 stimulus legislation.

What Did the Study Find?

SNAP benefits have a relatively stronger effect on the depth and severity 

of poverty than on the prevalence of poverty, and have a particularly strong 

alleviative effect on poverty among children, who experience significantly 

higher rates of poverty than the overall population. 

Specifically, we found that:

•	SNAP benefits led to an average annual decline of 4.4 percent in the

prevalence of poverty from 2000 to 2009, while the average annual 

decline in the depth and severity of poverty was much larger (10.3 and 

13.2 percent, respectively). 

•	When SNAP benefits are included in family income, the average annual

decline from 2000 to 2009 in the depth of child poverty was 15.5 

percent and the average annual decline in the severity of child poverty 

was 21.3 percent. 

•	SNAP benefits reduced the depth and severity of poverty in both metropolitan areas and nonmetropolitan areas, with somewhat greater poverty 

reductions among individuals in nonmetropolitan areas.
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SNAP’s antipoverty effect was strongest in 2009, when benefit increases 

were authorized by the American Recovery and Reinvestment Act (ARRA), 

also known as the stimulus package. In 2009, SNAP benefits:

•	Reduced the depth of child poverty by 20.9 percent and the severity of

child poverty by 27.5 percent. 

•	Ensured that the depth and severity of poverty in the overall population increased only slightly from their 2008 levels despite worsening 

economic conditions.

Our analysis shows that examining the basic poverty rate on its own leads to 

an understatement of the role of SNAP benefits in the reduction of poverty. 

Extending the analysis to include the poverty-gap and squared-poverty-gap 

indices adds to our understanding of the role SNAP plays in improving the 

welfare of individuals in low-income households. 

How Was the Study Conducted?

We used 10 years of cross-sectional data from the U.S. Census Bureau’s 

Annual Social and Economic Supplement to the Current Population Survey 

(CPS), a nationally representative sample of households that provides information on several different sources of income, including in-kind benefits 

such as SNAP. SNAP benefits are not included in the definition of family 

income used in the official U.S. poverty calculation. We added the value of 

SNAP benefits to family income, and compared several measures of annual 

poverty with and without SNAP benefits. We used the CPS for this analysis 

because it is the data source for official U.S. poverty estimation. A limitation 

of the CPS is that SNAP participation and benefits are under-reported in the 

survey, thus leading to an underestimate of SNAP’s effect on poverty.

To estimate the effect of SNAP on poverty, we examined how supplementing 

income with SNAP benefits affects the headcount, poverty-gap, and squaredpoverty-gap indices. The headcount is simply the proportion of persons 

living in poverty, or the poverty rate. The poverty-gap index measures the 

depth of poverty and is defined by the mean distance below the poverty 

threshold, where the mean is formed over the entire population (the nonpoor 

are counted as having zero poverty gap). The third measure is the squaredpoverty-gap index, which provides a measure of the severity of poverty, and 

is defined as the mean of the squared proportionate poverty gaps.
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Introduction

The Supplemental Nutrition Assistance Program (SNAP, formerly called 

the Food Stamp Program) is one of the largest means-tested social programs 

in the United States, providing total benefits of almost $72 billion in 2011. 

SNAP has experienced significant growth during the last decade. The 

average monthly SNAP caseload increased from 17.2 million individuals in 

2000 to 44.7 million individuals in 2011.

In light of the vital role of SNAP in the social safety net, it is worthwhile 

to examine the program’s effectiveness. Numerous studies have evaluated the effect of SNAP on outcomes such as food expenditures (Breunig 

and Dasgupta, 2005), food insecurity (DePolt et al., 2009; Gundersen et 

al., 2009; Gundersen and Oliveira, 2001; Kreider et al., forthcoming 2012; 

Nord and Prell, 2011; Ratcliffe and McKernan, 2011; Wilde and Nord, 

2005), diet quality and nutrition (e.g., Fox et al., 2004; Wilde et al., 1999) 

and obesity (Baum, 2011; Meyerhoefer and Pylypchuk, 2008; Ver Ploeg 

and Ralston, 2008). 

Previous research has also examined the effect of SNAP benefits, as well 

as other near-cash government benefits, on the poverty rate. Much of this 

research has been conducted as part of efforts to develop and assess alternatives to the official measure of U.S. poverty (Citro and Michael, 1995; Garner 

and Short, 2010; Iceland et al., 2001; Blank, 2008). This broad research 

effort has culminated in the development of the Research Supplemental 

Poverty Measure (SPM) by the U.S. Census Bureau, which complements the 

official poverty measure (Short, 2011).1 The SPM is designed to account for 

government expenditures that improve the well-being of low-income families, and has been used to calculate the number of individuals lifted above 

the poverty line by SNAP benefits (DeNavas-Walt et al., 2010; Short, 2011). 

Research in the United States tends to focus on the poverty rate, though 

recent studies have paid greater attention to how government transfers have 

decreased the aggregate poverty gap, or the sum of the differences between 

the poverty threshold and the incomes of the poor (Scholz et al., 2009; Ziliak, 

2005, 2008), and others have examined trends in the distribution of government transfers to different income classes and demographic groups among 

the poor (Moffitt and Scholz, 2010; Newman et al., 2011; Todd et al., 2010; 

Ziliak, 2008).

We contribute to this literature in three ways. First, we examine the effect of 

SNAP on measures that reflect the depth and severity of poverty as well as 

the poverty rate from 2000 to 2009, providing an update to previous research 

by Jolliffe et al. (2005) that examined the effect of SNAP on poverty in the 

1990s.2 Second, we consider poverty in the overall population and among 

two subpopulations—children and those living in nonmetropolitan areas—

who experience relatively high rates of poverty. Finally, we examine the 

antipoverty effect of the additional SNAP expenditures authorized by the 

American Recovery and Reinvestment Act (ARRA) of 2009, also known as 

the stimulus package.

1For more details on the Supplemental Poverty Measure, see http://www.

census.gov/hhes/povmeas/methodology/supplemental/overview.html/.

2Ziliak (2005) also considers trends 

in the depth and severity of poverty 

through 2003, after the inclusion of 

SNAP and other in-kind benefits.
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SNAP: Eligibility, Participation, and Benefits

SNAP is the largest U.S. food assistance program, providing 44.7 million 

individuals with an average monthly benefit of $134 in 2011. In contrast with 

many other programs serving low-income households, SNAP eligibility does 

not depend on family structure, age, or disability status, so benefits reach a 

broad range of disadvantaged households.3

To receive SNAP benefits, households must meet three financial criteria: 

the gross income, net income, and asset tests.4 A household’s gross income 

before taxes in the previous month must be at or below 130 percent of the 

poverty line, or $1,984 per month in fiscal year 2010 for a three-person 

household.5 (Federal fiscal years span October 1 through September 30 of 

the year listed). In addition to the gross income test, a household must have 

net monthly income at or below the poverty line.6 Finally, income-eligible 

households must have assets less than $2,000 ($3,000 for households with a 

household member who is over age 60 or disabled).

The SNAP benefit formula is a function of the maximum SNAP benefit 

amount (also known as the benefit guarantee) and the household’s net 

income. Households with no net income receive the maximum SNAP benefit, 

based on the estimated cost of a nutritionally adequate diet for a given household size.7 The SNAP benefit reduction rate is 30 percent—benefits are 

reduced by 30 cents for each additional dollar in household net income—and 

therefore, the poorest SNAP households receive the largest benefits. 

The number of people participating in SNAP has grown steadily from 2000 

to 2009 (fig. 1). Figure 1 also shows that, historically, SNAP has been a 

countercyclical program; the caseload increases during recessionary times 

and declines during economic expansions (Mabli et al., 2009; Ziliak et al., 

2003). One notable exception was during the period of economic growth 

after the 2001 recession, when the unemployment rate dropped, but the 

SNAP caseload continued to increase. The poverty rate continued to increase 

during this time period, which may help to explain the caseload increase. 

There are also a number of changes in SNAP policy that have occurred over 

the past decade that may have contributed to the caseload increase. States 

have been granted increased flexibility in how they administer SNAP, in an 

effort to increase program access and reduce administrative burden (GAO, 

2002). Many of the changes are designed to increase SNAP participation 

among working poor households. For example, States have been given the 

option to exempt the value of one or more household vehicles from the 

calculation of a household’s assets (USDA/FNS, 2009).8 States have also 

implemented a number of program changes to simplify the administrative 

process to apply for and remain on SNAP (GAO, 2002). 

As the caseload increased from 2000 to 2009, total SNAP benefits also 

increased (table 1). Real average benefits per person increased somewhat 

from 2000 to 2008, and then jumped by 20 percent from 2008 to 2009, when 

the 2009 ARRA increased SNAP benefit levels. 

3There are certain restrictions placed 

on legal immigrants and able-bodied 

adults without dependents who apply 

for SNAP payments.

4SNAP eligibility guidelines are available at: http://www.fns.usda.gov/snap/

applicant_recipients/eligibility.htm/.

5Households with a household 

member who is over the age of 60 are 

exempt from the gross income test.

6Net income is equal to gross income 

minus a number of deductions. These 

deductions are a standard deduction, 

as well as deductions for labor market 

earnings (up to 20 percent of earnings), 

child care expenses, expenses for medical care of disabled dependents, and 

shelter costs in excess of 50 percent of 

a household’s net income.

7For more details on the SNAP benefit formula, see: http://www.fns.usda.

gov/snap/applicant_recipients/

eligibility.htm/.

8The Federal asset test requires that 

the market value of a vehicle over 

$4,650 be counted as part of the household’s assets. 
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Figure 1

SNAP participants, people in poverty, and the unemployment rate, 1980-2009

SNAP = Supplemental Nutrition Assistance Program.

Source: USDA, Economic Research Service calculations based on data from USDA, Food and Nutrition Service, U.S. Census Bureau, 

and U.S. Bureau of Labor Statistics.

1980 82 84 86 88 90 92 94 96 98 2000 02 04 06 08

0

5

10

15

20

25

30

35

40

45

50

0

2

4

6

8

10

12

14

16

18

20

SNAP participants

People in poverty

Unemployment rate

Millions of people Percent of U.S. labor force

Table 1

SNAP benefits: Total, average monthly per person, and distribution 

across poverty levels, 2000-09

Year

Total SNAP

benefits

Average monthly 

SNAP benefit 

per person

Poor 

households

Households in 

deep poverty

2009 dollars

(billions) 2009 dollars Percent of SNAP benefits received

2000 11.6 94.12 95.7 53.7

2001 12.4 94.05 95.9 55.1

2002 14.8 98.35 95.6 56.8

2003 17.7 101.45 95.7 58.2

2004 21.0 100.57 95.0 57.1

2005 25.0 105.67 95.0 56.8

2006 27.1 105.19 94.3 56.3

2007 28.3 102.66 94.6 56.1

2008 33.4 105.12 94.5 58.3

2009 50.4 124.25 93.0 55.8

Note: Deep poverty is defined as having income below 50 percent of the Federal poverty 

guidelines.

SNAP = Supplemental Nutrition Assistance Program.

Source: USDA, Economic Research Service calculations based on USDA, 

Food and Nutrition Service data.
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The ARRA increased the maximum SNAP benefit by 13.6 percent over the 

fiscal year 2008 level, effective April 2009, but did not change the SNAP 

benefit reduction rate. In other words, the ARRA shifted up the intercept 

of the SNAP benefit formula, but did not change its slope with respect to 

household net income. Households of the same size received the same dollar 

increase in SNAP benefits, regardless of their net income. For example, 

the maximum monthly benefit level for a three-person SNAP household 

increased from $463 to $526 starting in April 2009, resulting in a $63 

increase in monthly SNAP benefits for all three-person SNAP households.9

Table 1 also provides evidence of the targeting of SNAP benefits to poor 

households. According to USDA administrative data, over 90 percent 

of SNAP benefits were received by poor households and over half were 

received by households with income less than 50 percent of the Federal 

poverty guidelines. While real total SNAP benefits more than quadrupled 

from 2000 to 2009, the share of total benefits received by the poor and the 

severely poor remained fairly steady over the time period.

9The exceptions are one- and twoperson SNAP households receiving the 

minimum benefit, which increased from 

$14 to $16 per household per month 

under the ARRA.
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The Current Population Survey Data

To measure the effect of SNAP on poverty, we used data from the Annual 

Social and Economic (ASEC) Supplement to the Current Population 

Survey (CPS) conducted by the U.S. Census Bureau. We used 10 years 

of CPS-ASEC data from 2001 to 2010, which provided us with estimates 

of poverty and SNAP benefit levels from 2000 to 2009. The CPS is 

administered monthly by the U.S. Census Bureau for the U.S. Department 

of Labor’s Bureau of Labor Statistics and collects data from a nationally 

representative sample of households on employment, unemployment, 

earnings, occupation, and hours of work. Respondents to the CPS provide 

information on several different sources of income, including noncash 

income sources such as SNAP. 

We used the CPS because it is the data source for official U.S. poverty 

estimation, and our analysis focused on how SNAP affects poverty. We 

considered the effect of adding the value of SNAP benefits to family 

income and compare several measures of poverty with and without SNAP 

benefits. We were particularly concerned about matching the official poverty 

estimates, and the CPS allowed us to do this.

A shortcoming of the CPS is that, as recently documented by Meyer et al. 

(2009), it underestimates the number of SNAP recipients and the value of 

SNAP benefits. We found that, from 2000 to 2009, the reported average 

monthly individual participation in the CPS was 70.6 percent of the average 

monthly individual participation in SNAP administrative data and the 

reported total benefits in the CPS were 59.3 percent of administrative totals. 

The under-reporting of SNAP receipt is not unique to the CPS, as shown by 

Bollinger and David (1997) and Meyer et al. (2009). One common approach 

to correct for under-reporting of program participation is to predict receipt, 

based on the observable characteristics of participants. (See, for example, 

Scholz et al. (2009).) However, recent research using SNAP administrative 

data in two States matched with CPS data suggested that there are systematic 

differences in the characteristics of SNAP participants who correctly report 

participation and those who do not (Meyer and Goerge, 2011). Although 

we did not correct for the under-reporting of SNAP receipt in this analysis, 

future research could incorporate the information on SNAP receipt gained 

from efforts to match survey and administrative data across a larger share of 

the U.S. population. We consider the implications of the under-reporting of 

SNAP benefits in our discussion of the results.
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Measures of Poverty

The official U.S. poverty measure is based on a comparison of a family’s 

income relative to its needs. The income measure includes all pre-tax 

income, such as earnings, unemployment compensation, and Social Security 

payments. It also includes cash benefits from means-tested transfer programs 

such as Supplemental Security Income (SSI) and Temporary Assistance for 

Needy Families (TANF). The measure does not include unrealized capital 

gains, and because it is a pre-tax measure, it does not include Earned Income 

Tax Credit (EITC) payments. Of particular relevance for this analysis, 

the family income measure does not include any noncash benefits such 

as SNAP benefits, housing assistance, or Medicaid. The family-income 

measure includes income of all family members in a household, but excludes 

income of nonrelatives, such as unmarried cohabitators.10 A family’s need is 

measured by the poverty threshold, based on a cost-of-basic-needs methodology. The U.S. Federal poverty thresholds vary for persons of different ages 

and families of different sizes. In 2010 for example, the poverty threshold 

was set at $11,369 for an individual under 65 years of age, $15,063 for a twoperson family with one child and one adult, and $26,080 for a family with 

two adults and three children.11

If family income is less than the poverty threshold, then all members of the 

family are considered poor. The rate of poverty (or headcount index) is then 

the proportion of individuals living in poor families relative to the total population. The rate of child poverty is the proportion of children living in poor 

families relative to the total number of children in the population. We similarly computed the other poverty indices by assigning to each person their 

family’s income and poverty threshold. 

To understand the effect of SNAP on poverty, we examined how supplementing income with SNAP benefits affects the headcount, poverty-gap, and 

squared-poverty-gap indices.12 These three measures are from the frequently 

used Foster-Greer-Thorbecke (1984, hereafter referred to as FGT) family of 

poverty indices. The headcount is simply the proportion of persons living 

in poverty, or the prevalence of poverty. The poverty-gap index measures 

the depth of poverty and is defined by the mean distance below the poverty 

threshold, where the mean is formed over the entire population (the nonpoor 

are counted as having zero poverty gap). The third measure is the squaredpoverty-gap index, which provides a measure of the severity of poverty, and 

is defined as the mean of the squared proportionate poverty gaps.

The FGT class of poverty indices, also referred to as Pa , can be represented 

as: 

(1) i i i P 1 n I(y z)[(z y ) z]a

a = <− ∑

where n is the sample size, i subscripts the individual or family, y is income, 

z is the poverty threshold, and I is an indicator function which takes the value 

of one if the statement is true and zero otherwise. When α=0, the resulting 

measure is the headcount index, or P0. When α=1, the FGT index results in 

the poverty-gap index, or P1 and the squared-poverty-gap index (P2) results 

when α=2. 

10Because we considered the official 

poverty measure, our analysis estimated 

the effect of SNAP on poverty in the 

absence of income sources, such as 

the EITC, that are not included in the 

official income measure. 

11For a complete listing of the 

poverty thresholds for individuals and 

families of various sizes, see the U.S. 

Census Bureau’s web page on poverty 

at: http://www.census.gov/hhes/www/

poverty.html/.

12We assumed that a household’s 

SNAP benefits are equivalent to cash. 

Research suggests that this is a reasonable assumption, given that the typical 

SNAP household’s expenditures on 

food are greater than the household’s 

SNAP benefit (Hoynes and Schanzenbach, 2009).
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The usefulness of these measures can be illustrated by considering a transfer 

of money from a nonpoor person to a poor person that is not large enough to 

move the poor person above the poverty threshold. This transfer has no effect 

on the headcount index, but the poor person is better off and this welfare 

improvement is reflected in a reduction of both the poverty-gap and squaredpoverty-gap indices. 

The difference between the poverty-gap index and the squared-povertygap index can be illustrated by considering two possible transfers of 

equal amounts from a nonpoor person. The first is a transfer to a poor 

person whose income is equal to 50 percent of the poverty threshold and 

the second is a transfer to a poor person with higher income, equal to 75 

percent of the poverty threshold. Again, the transfers are not enough to lift 

either person above the poverty threshold and therefore neither transfer 

will reduce the poverty rate. Since the transfers are of equal amounts, they 

will each reduce the poverty-gap index by the same amount. However, 

the squared poverty gap will be reduced more by the first transfer, which 

is received by a relatively poorer person, than by the second transfer. In 

general, the lower the income of the poor person who receives a transfer 

from a nonpoor person, the greater will be the effect on the squaredpoverty-gap index.13 (See box “How Government Transfers Can Reduce 

the Depth and Severity of Poverty” for more detailed information on the 

poverty-gap and squared-poverty-gap indices.)

These examples point to an important reason to consider the poverty-gap 

and squared-poverty-gap indices in addition to the commonly reported headcount index. As discussed above, SNAP benefits are inversely related to net 

income, and as a consequence, adding benefits to income will raise only a 

small subset of recipients above the poverty threshold. However, the progressive benefit delivery design will be relatively more effective at reducing the 

depth and severity of poverty than at reducing the prevalence of poverty.

It is important to note that we did not capture the potential behavioral 

response to SNAP benefits. If SNAP benefits reduce an individual’s labor 

supply (the amount of time spent working), then earned income will be 

lower than it would have been in the absence of SNAP and we would 

overstate the effect of SNAP on total family income. Research suggests, 

however, that the labor supply response to SNAP benefits is small (Fraker 

and Moffitt, 1988; Hagstrom, 1996; Hoynes and Schanzenbach, 2010; 

Keane and Moffitt, 1998).

To examine the efficacy of SNAP benefits in reducing poverty, one needs 

both measures of poverty and measures of their sampling variance in order to 

know if changes in poverty are statistically significant or simply an artifact of 

the sampling procedure. We estimated the variance of Pa, using an estimation 

technique that accounted for the fact that the CPS data were not derived from 

a simple random sample.14

13Unlike the Sen (1976) or Kakwani 

(1980) poverty indices, the squaredpoverty-gap index also satisfies 

“subgroup consistency,” which 

means that if poverty increases in 

any subgroup, and does not decrease 

elsewhere, then aggregate poverty must 

increase (Foster and Shorrocks, 1991).

14Kish (1965) and Howes and 

Lanjouw (1998) provide evidence of the 

importance of correcting for deviations 

from a simple random sample design. 

Further details on the method employed 

to estimate the sampling variance are 

provided in Jolliffe and Semykina 

(1999), Jolliffe (2002/2003), and 

Jolliffe et al. (2005).
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How Government Assistance Can Reduce 

the Depth and Severity of Poverty

A simple example can help to explain how the poverty-gap index and the 

squared-poverty-gap index are affected by anti-poverty programs. Consider a 

community with two poor people—Alice and Ralph—and eight nonpoor people. 

The poverty threshold is $11,000 per year, Alice’s pre-transfer annual income 

is $8,000, and Ralph’s pre-transfer annual income is $5,000. In the absence of 

government assistance, the poverty rate is 20 percent. The poverty-gap index is 

8.2 and the squared-poverty-gap index is 3.7. The aggregate poverty gap—the 

total amount of money that would need to be transferred to the poor in order to 

lift all poor people out of poverty—is $9,000.

Under Scenario A, each poor person receives $1,000 in government assistance 

each year, so Alice’s post-transfer annual income is $9,000 and Ralph’s posttransfer annual income is $6,000.1 Neither person’s income is raised above the 

poverty threshold, so the poverty rate does not change; 20 percent of people in 

the community are poor. However, the depth and severity of poverty are both 

reduced. Notice that the aggregate poverty gap has been reduced to $7,000.

Under Scenarios B and C, only one person receives government assistance. 

Under Scenario B, Alice receives $2,000 and Ralph receives no government 

assistance, and under Scenario C, Alice receives no government assistance and 

Ralph receives $2,000. In both Scenarios B and C, the aggregate poverty gap 

and the depth of poverty are reduced by equal amounts. However, the severity 

of poverty is reduced more in Scenario C than in Scenario B, reflecting the fact 

that the severity measure is more sensitive to income changes among the poorest 

of the poor.

1We assume that the government transfers do not result in any nonpoor person being 

moved below the poverty line.

How anti-poverty programs affect the poverty-gap index and the 

squared-poverty-gap index—hypothetical scenarios

Pretransfer 

income

Posttransfer 

income

Poverty 

rate

Aggregate 

poverty 

gap

Depth of 

poverty1

Severity 

of 

poverty2

Original

Alice $8,000 20 

percent $9,000 8.2 3.7

Ralph $5,000

Transfer 

Scenario A

Alice $8,000 $9,000 20 

percent $7,000 6.4 2.4

Ralph $5,000 $6,000

Transfer 

Scenario B

Alice $8,000 $10,000 20 

percent $7,000 6.4 3.1

Ralph $5,000 $5,000

Transfer 

Scenario C

Alice $8,000 $8,000 20 

percent $7,000 6.4 2.1

Ralph $5,000 $7,000

Note: All poverty indices are multiplied by 100.

1Poverty-gap index.

2Squared-poverty-gap index.
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The Effect of SNAP Benefits on Poverty

We estimated poverty and child poverty rates from 2000 to 2009, reported in 

table 2. These estimates use income (but do not include SNAP benefits) and 

form a baseline for comparison with later tables (which do include SNAP 

benefits). Table 2 verifies the well-known result that the proportion of children living in poverty, or the child headcount index, is much higher than 

for the entire population. For example, in 2009, 20.7 percent of all children 

were poor versus 14.3 percent of all persons. Between 2000 and 2009, the 

child headcount index was on average 41.4 percent higher than the headcount 

index for the population, and the difference was statistically significant in all 

years.15 Table 2 also shows that the poverty-gap and squared-poverty-gap 

indices are higher for children than for the total population. For example, in 

2009 the poverty-gap index was 42.9 percent higher for children than for all 

people, and the squared-poverty-gap index was 38.8 percent higher for children than for all people. Thus, not only are children more likely to be poor 

than the overall population, poor children are disproportionally represented at 

the lower end of the income distribution among the poor.

15We follow Howes and Lanjouw 

(1998) to correct the standard 

errors and test for differences in P0, 

P1, and P2. Over the 10 years, and for 

all three poverty measures, the child 

poverty rate is higher than the overall 

poverty rate with p-values that are 

much less than 0.0001. 

Table 2

Rates of poverty and child poverty, 2000-09

Headcount index Poverty gap Squared poverty gap

Year Persons Children Persons Children Persons Children

2000 11.3 16.1 5.1 7.2 3.4 4.6

(0.18) (0.38) (0.10) (0.21) (0.08) (0.16)

2001 11.7 16.3 5.4 7.7 3.8 5.2

(0.15) (0.29) (0.08) (0.17) (0.07) (0.14)

2002 12.1 16.7 5.6 7.6 3.9 5.0

(0.15) (0.29) (0.08) (0.16) (0.07) (0.13)

2003 12.5 17.6 6.0 8.4 4.2 5.7

(0.15) (0.30) (0.09) (0.18) (0.08) (0.15)

2004 12.7 17.8 6.1 8.4 4.3 5.6

(0.15) (0.31) (0.09) (0.18) (0.08) (0.15)

2005 12.6 17.6 6.1 8.4 4.3 5.7

(0.15) (0.31) (0.09) (0.18) (0.07) (0.15)

2006 12.3 17.4 5.9 8.2 4.1 5.5

(0.15) (0.30) (0.09) (0.18) (0.07) (0.15)

2007 12.5 18.0 5.9 8.5 4.1 5.7

(0.15) (0.31) (0.09) (0.18) (0.07) (0.15)

2008 13.2 19.0 6.4 9.2 4.5 6.3

(0.16) (0.31) (0.09) (0.19) (0.08) (0.16)

2009 14.3 20.7 7.0 10.0 4.9 6.8

(0.16) (0.32) (0.10) (0.20) (0.08) (0.16)

Note: All poverty indices are multiplied by 100. The first column under each of the three 

indices lists the poverty rates for all people and the second column lists the child poverty rates. 

Estimates are based on Current Population Survey March Supplement data and standard 

errors (in parentheses) are corrected for sample-design effects following Jolliffe (2002/03).

Source: USDA, Economic Research Service calculations based on Current Population Survey 

Annual Social and Economic Supplement data.
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Table 3 reports the same poverty measures introduced in table 2, but focuses 

on a comparison of metropolitan areas with nonmetropolitan areas, with results 

from every other year from 2001 to 2009.16 Table 3 shows that, consistent 

with previous research, the prevalence of poverty is higher among persons in 

nonmetropolitan areas than among those in metropolitan areas (DeNavas-Walt 

et al., 2010; Jolliffe, 2003). In addition, we found that the depth and severity 

of poverty were consistently higher in nonmetropolitan areas than in metropolitan areas (though the metro-nonmetro difference in the severity of poverty 

was statistically insignificant at conventional levels in 3 of the 10 years of the 

analysis).17 The same relationships hold for children; child poverty is higher in 

nonmetropolitan than in metropolitan areas across all three poverty measures. 

These results indicate that poverty is more prevalent in nonmetropolitan areas, 

and the nonmetropolitan poor are more likely than the metropolitan poor to be 

at the lower end of the income distribution of the poor.18

16This analysis could also be 

extended to other population groups, 

such as those based on family structure 

and race/ethnicity as in Gundersen and 

Ziliak (2004). 

17Jolliffe (2003) finds that the 

annual differences in the depth and 

severity of poverty between metro and 

nonmetro areas are much less likely to 

be statistically significant during the 

1990s. The metro-nonmetro difference 

in the poverty gap is statistically 

significant in only 6 of the 10 years and 

the squared poverty gap is statistically 

significant in only 3 of the 10 years.

18Adjusting for geographic 

differences in housing costs has been 

shown to reduce the poverty rate in 

nonmetropolitan areas and to increase 

the poverty rate in metropolitan areas 

(Jolliffe, 2006; Short, 2011). Jolliffe 

(2006) also finds reductions in the 

depth and severity of nonmetropolitan 

poverty and increases in the depth and 

severity of metropolitan poverty after 

adjusting for housing cost differences. 

While data constraints did not allow 

us to incorporate the changes in 

poverty measurement introduced in the 

Research SPM for our study period, this 

is an important area of future research.

Table 3

Poverty and child poverty indices in metro and nonmetro areas, 

2001-09

Year Area

Headcount Poverty gap

Squared 

poverty gap

Persons Children Persons Children Persons Children

2001 Metro 11.1 15.4 5.2 7.3 3.6 4.9

(0.16) (0.32) (0.09) (0.19) (0.08) (0.15)

Non-metro 14.2 20.2 6.3 9.7 4.3 6.7

(0.34) (0.70) (0.20) (0.46) (0.17) (0.39)

2003 Metro 12.1 17.1 5.9 8.2 4.2 5.6

(0.17) (0.33) (0.10) (0.20) (0.08) (0.17)

Nonmetro 14.2 20.1 6.4 9.2 4.3 6.1

(0.34) (0.68) (0.19) (0.39) (0.15) (0.33)

2005 Metro 12.2 17.2 5.9 8.2 4.2 5.5

(0.17) (0.34) (0.10) (0.20) (0.08) (0.16)

Nonmetro 14.4 19.8 6.9 9.7 4.7 6.6

(0.35) (0.72) (0.21) (0.45) (0.18) (0.39)

2007 Metro 11.9 17.2 5.7 8.1 4.0 5.5

(0.17) (0.34) (0.10) (0.20) (0.08) (0.17)

Nonmetro 15.4 22.1 7.0 10.4 4.8 7.0

(0.38) (0.76) (0.22) (0.46) (0.18) (0.38)

2009 Metro 13.9 20.2 6.8 9.8 4.8 6.7

(0.18) (0.36) (0.11) (0.22) (0.09) (0.18)

Nonmetro 16.6 23.5 7.7 11.1 5.3 7.5

(0.39) (0.77) (0.22) (0.46) (0.18) (0.38)

Note: All poverty indices are multiplied by 100. The first column under each of the three 

indices lists the poverty rates for all people and the second column lists the child poverty 

rates. For each year, the first row lists the poverty rates for the metropolitan population 

(persons and children) and the second rows list the poverty rates for the nonmetropolitan 

population. Standard errors for all poverty estimates are corrected for sample-design effects 

following Jolliffe (2002/03) and are in parentheses. Odd years only are listed due to space 

considerations; results in the even years are consistent with those presented for the odd 

years.

Source: USDA, Economic Research Service calculations based on Current Population Survey 

Annual Social and Economic Supplement data.
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SNAP Impact Is Stronger on Reducing Depth and 

Severity of Poverty Than Prevalence of Poverty

Our next step is to examine the impact of SNAP on poverty.19 Table 4 

lists poverty rates for each of the three poverty measures with the value of 

SNAP benefits added to family income. More precisely, the columns labeled 

“Income + SNAP” in table 4 report: 

(2) i i i i i P 1 n I({y fsb } z)[(z {y fsb }) z]a

a

′ = + < −+ ∑

where fsbi is the value of SNAP benefits for family i, and all other terms are 

defined as in equation (1). The next column reports the percentage decline 

in poverty from including SNAP benefits, [(Pa - P ́a )/ Pa ]*100; in other 

words the percentage difference between the results from equation (2) and 

19We note that our primary analysis 

focused on families below the poverty threshold. Therefore, we did not 

capture improvements in well-being 

among SNAP recipients with family 

income above the poverty threshold. 

Among SNAP recipients in fiscal year 

2009, 10.9 percent had gross income 

above the poverty guidelines (Leftin 

et al., 2010). We conducted additional 

analysis of the effect of SNAP on poverty, where a family is considered poor 

if its income is below 130 percent of 

the official poverty threshold, which 

closely matches SNAP gross income 

eligibility guidelines. Using this higher 

poverty threshold, we found that SNAP 

had a relatively smaller effect on the 

headcount index, as shown in appendix 

table 1. This is not surprising, given 

that SNAP benefits continue to taper off 

as income increases.

Table 4

Poverty and SNAP benefits, 2000-09

Percentage reduction in poverty from SNAP benefits

Headcount Poverty gap Squared poverty gap

Year Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent

decline

2000 10.9 3.1 4.6 8.6*** 3.0 11.3***

(0.18) (2.23) (0.09) (2.55) (0.07) (3.02)

2001 11.3 3.2* 5.0 8.4*** 3.4 11.0***

(0.14) (1.73) (0.08) (2.03) (0.06) (2.40)

2002 11.7 3.1* 5.1 8.6*** 3.4 11.3***

(0.15) (1.69) (0.08) (1.91) (0.06) (2.23)

2003 12.0 3.6** 5.4 9.5*** 3.7 12.3***

(0.15) (1.68) (0.08) (1.93) (0.07) (2.27)

2004 12.2 4.4*** 5.5 9.9*** 3.7 12.9***

(0.15) (1.66) (0.08) (1.90) (0.07) (2.23)

2005 12.1 4.4*** 5.4 10.5*** 3.7 13.3***

(0.15) (1.66) (0.08) (1.88) (0.07) (2.18)

2006 11.7 4.5*** 5.3 10.2*** 3.6 13.0***

(0.15) (1.68) (0.08) (1.94) (0.07) (2.27)

2007 11.9 4.3** 5.3 10.7*** 3.6 13.5***

(0.15) (1.69) (0.08) (1.91) (0.07) (2.23)

2008 12.5 5.2*** 5.6 11.8*** 3.8 14.8***

(0.15) (1.62) (0.08) (1.83) (0.07) (2.13)

2009 13.2 7.7*** 5.9 14.6*** 4.0 18.0***

(0.16) (1.52) (0.08) (1.69) (0.07) (1.94)

Mean:

2000-09 12.0 4.4 5.3 10.3 3.6 13.2

Note: All poverty indices are multiplied by 100. The first column under each of the three poverty 

indices lists the poverty estimates with SNAP benefits added to income. Standard errors for all 

poverty estimates are corrected for sample-design effects following Jolliffe (2002/03) and are 

in parentheses. The second column under each of the poverty measures lists the percentage 

decline in the poverty index from the SNAP benefits. The estimated percent reduction is superscripted with *, **, or *** if the p-value is less than 0.1, 0.05, or 0.01, respectively. Standard 

errors for the percent decline are listed in parentheses and are second-order approximations.

SNAP = Supplemental Nutrition Assistance Program.

Source: USDA, Economic Research Service calculations based on Current Population Survey 

Annual Social and Economic Supplement data.
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equation (1). Because the interpretation of the values of the poverty-gap and 

squared-poverty-gap indices are not as straightforward as the interpretation 

of the value of the headcount index, we compare the percent declines in each 

of the indices in order to assess SNAP’s effect on each. Standard errors for 

the relative decline in poverty are estimated as a second-order Taylor series 

expansion.

20

As shown in table 4, the percentage of individuals lifted above the poverty 

threshold by SNAP benefits increased fairly steadily through 2008. The decline 

in the headcount index from SNAP benefits was 3.1 percent in 2000 and rose 

to 5.2 percent in 2008. In 2009, the decline in the headcount index from SNAP 

benefits jumped to 7.7 percent, when SNAP benefits were increased through 

the ARRA. The decline in the headcount index of 7.7 percent means that the 

supplemented income brought approximately 3.4 million people over the 

poverty threshold. This change is qualitatively significant, but given that in 

2009 there were over 43.6 million poor people, the change in the headcount 

index failed to measure much of the poverty alleviation properties of SNAP 

benefits. In contrast, the estimates in table 4 reveal that both the poverty gap 

and squared poverty gaps were changed considerably by the inclusion of SNAP 

benefits.21 From 2000 to 2009, supplementing income by the value of SNAP 

benefits had the effect of reducing the poverty-gap index by an average of 10.3 

percent and reducing the squared-poverty-gap index by an average of 13.2 

percent. These poverty reductions were much greater than when just considering the change in the headcount index, which was reduced by the inclusion of 

SNAP benefits by an average of 4.4 percent from 2000 to 2009. 

The addition of SNAP benefits to income does relatively less to decrease the 

prevalence of poverty, P0, because benefits are negatively related to income. 

In general, only a subset of poor households will have income close enough 

to the poverty threshold to allow SNAP benefits to actually lift them above 

the threshold, and Leftin (2010) shows that SNAP participation rates of 

eligible households with higher incomes are lower than for poorer households. Therefore, not only is the effect of SNAP benefits on the headcount 

index limited to a proportion of poor SNAP participants whose income is 

closest to the poverty threshold, these are the households that are relatively 

less likely to participate. In contrast, lower income poor households have 

higher participation rates, but the addition of the value of SNAP benefits to 

their income is unlikely to lift them out of poverty and will therefore have no 

impact on the headcount index (though it will reduce the P1 and P2 indices).22

The evidence that SNAP is more effective at reducing the depth and severity 

of poverty than the prevalence of poverty is even stronger when we considered children in poor families. Table 5 shows that SNAP benefits in the first 

decade of the 2000s reduced the child poverty headcount by an average of 

5.6 percent, while reducing the child-poverty-gap index by an average of 

15.5 percent and the child-squared-poverty-gap index by an average of 21.3 

percent.23 The substantial reduction in the severity of child poverty from 

SNAP benefits illustrates that program benefits are targeted to children in the 

poorest of poor families.

20For details of the Taylor series approximation methodology, see Wolter 

(1985) and for an application to the 

decline in poverty, see Jolliffe et al. 

(2005).

21One interpretation of the povertygap index is that it equals the product 

of the headcount index and the income 

gap, where the income gap is the average shortfall of the poor as a fraction 

of the poverty line. The results indicate 

that, for example, in 2009, the average 

shortfall of the poor was 49.0 percent of 

the poverty line but when supplemented 

with SNAP benefits, the average 

shortfall declined to 44.6 percent of 

the poverty line. Table 2 shows that in 

2009, the headcount index was 14.3 and 

the poverty gap was 7.0. Therefore, the 

average shortfall of the poor was 7.0 

divided by 14.3, or 49 percent. After 

accounting for SNAP benefits, table 4 

shows that the average shortfall of the 

poor in 2009 was equal to 5.9 divided 

by 13.2, or 44.6 percent.

22We also examined the effect 

of SNAP on poverty, where a family is considered poor if its income 

is below 130 percent of the official 

poverty threshold, which more closely 

matches SNAP gross income eligibility 

guidelines. Using this higher poverty 

threshold, we found that SNAP has a 

relatively smaller effect on the headcount index, as shown in appendix table 

1. This is not surprising, given that 

SNAP benefits continue to taper off as 

income increases.

23Because poverty is measured at 

the family level, if family income plus 

SNAP benefits are greater than the poverty threshold, all children in the family 

are lifted out of poverty.
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SNAP Effect on Poverty Levels Is Underestimated in CPS

In our discussion of the CPS, we noted the serious underestimate of both 

the number of SNAP participants and the total dollar benefits received by 

participants in the data. The underestimate of participants and benefits would 

be expected to produce an underestimate of the antipoverty effect of SNAP 

across all three poverty measures. Therefore, our estimates can be thought of 

as a lower bound on the antipoverty effect of SNAP. In addition, we found that 

the proportion of total benefits received by participants with incomes below 50 

percent of the poverty line was much greater in the SNAP administrative data 

than in the CPS. This suggests that the underestimate of the antipoverty effect of 

SNAP may be particularly acute for the depth and severity of poverty measures. 

Thus, we would expect that a more accurate accounting of SNAP recipients and 

benefits in the CPS would further bolster our argument that SNAP is relatively 

Table 5

Child poverty and SNAP benefits, 2000-09

Percentage reduction in child poverty from SNAP

Year

Headcount Poverty gap Squared poverty gap

Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent 

decline

Income 

+ SNAP

Percent 

decline

2000 15.4 3.9 6.2 13.0*** 3.8 18.4***

(0.37) (3.21) (0.18) (3.58) (0.14) (4.20)

2001 15.6 4.1* 6.7 12.8*** 4.3 17.9***

(0.29) (2.45) (0.16) (2.81) (0.12) (3.27)

2002 16 4.1* 6.6 13.5*** 4.1 19.1***

(0.29) (2.39) (0.14) (2.63) (0.11) (3.03)

2003 16.8 4.5* 7.2 14.4*** 4.5 20.1***

(0.30) (2.34) (0.16) (2.64) (0.13) (3.06)

2004 16.7 5.8** 7.1 15.3*** 4.4 21.8***

(0.30) (2.33) (0.16) (2.65) (0.13) (3.08)

2005 16.6 5.5** 7.1 15.9*** 4.4 21.8***

(0.30) (2.36) (0.16) (2.58) (0.12) (2.96)

2006 16.4 5.8** 7 15.3*** 4.4 20.9***

(0.29) (2.34) (0.16) (2.65) (0.13) (3.10)

2007 17.0 5.6** 7.1 16.1*** 4.5 21.8***

(0.31) (2.36) (0.16) (2.63) (0.13) (3.06)

2008 17.8 6.3*** 7.6 17.3*** 4.8 23.2***

(0.31) (2.25) (0.17) (2.47) (0.13) (2.85)

2009 18.7 9.8*** 7.9 20.9*** 4.9 27.5***

(0.31) (2.07) (0.16) (2.26) (0.13) (2.58)

Mean:

2000-09 16.7 5.6 7.1 15.5 4.4 21.3

Note: All poverty indices are multiplied by 100. The first column under each of the three poverty 

indices lists the poverty estimates with SNAP benefits added to income. Standard errors for all 

poverty estimates are corrected for sample-design effects following Jolliffe (2002/03) and are 

in parentheses. The second column under each of the poverty measures lists the percentage 

decline in the poverty index from the SNAP benefits. The estimated percent reduction is superscripted with *, **, or *** if the p-value is less than 0.1, 0.05, or 0.01, respectively. Standard 

errors for the percent decline are listed in parentheses and are second-order approximations.

SNAP = Supplemental Nutrition Assistance Program.

Source: USDA, Economic Research Service calculations based on Current Population Survey 

Annual Social and Economic Supplement data.
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more effective at reducing the depth and severity of poverty than the prevalence 

of poverty. As noted previously, the development of methods to correct for the 

underreporting of program participation and benefits could be useful to improve 

future assessments of the antipoverty effect of SNAP.

Table 6 examines how the addition of SNAP benefits to income affects the 

measures of the prevalence, depth, and severity of poverty in metropolitan 

and nonmetropolitan areas. Our findings are consistent with those from 

tables 4 and 5; SNAP has a greater effect on the depth and severity than on 

the prevalence of poverty in both metropolitan and nonmetropolitan areas, 

and the effect of SNAP on the three poverty measures generally increased 

from 2000 to 2009. Comparing metropolitan and nonmetropolitan areas 

Table 6

Metro and nonmetro poverty and SNAP benefits, 2001-09

Percentage reduction in poverty from SNAP benefits

Year Area

Headcount Poverty gap Squared poverty gap

Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent

decline

2001 Metro 10.7 3.3* 4.8 8.2*** 3.3 10.6***

(0.16) (2.00) (0.09) (2.32) (0.07) (2.73)

Nonmetro 13.8 2.8 5.7 9.5** 3.7 12.6**

(0.34) (3.32) (0.19) (4.08) (0.15) (4.96)

2003 Metro 11.6 3.6* 5.3 9.1*** 3.7 11.8***

(0.17) (1.92) (0.09) (2.20) (0.08) (2.56)

Nonmetro 13.7 3.5 5.7 11.1*** 3.7 14.6***

(0.33) (3.29) (0.17) (3.70) (0.14) (4.39)

2005 Metro 11.7 4.5** 5.3 10.2*** 3.6 12.9***

(0.16) (1.88) (0.09) (2.12) (0.07) (2.45)

Nonmetro 13.9 3.8 6.1 11.7*** 4.0 15.2***

(0.34) (3.32) (0.19) (3.85) (0.16) (4.57)

2007 Metro 11.4 4.3** 5.1 10.4*** 3.5 13.1***

(0.16) (1.93) (0.09) (2.17) (0.07) (2.53)

Nonmetro 14.7 4.4 6.2 11.8*** 4.0 15.3***

(0.37) (3.37) (0.19) (3.90) (0.16) (4.59)

2009 Metro 12.9 7.6*** 5.9 14.0*** 4.0 17.4***

(0.17) (1.72) (0.09) (1.91) (0.08) (2.18)

Nonmetro 15.2 8.2*** 6.4 17.1*** 4.2 21.2***

(0.37) (3.12) (0.19) (3.45) (0.16) (4.02)

10 yr.

mean

Metro 11.5 4.3 5.2 9.9 3.5 12.7

Nonmetro 14.0 4.6 5.9 11.8 3.8 15.3

Note: All poverty indices are multiplied by 100. The first column under each of the three 

poverty indices lists the poverty estimates with SNAP benefits added to income. Standard 

errors for all poverty estimates are corrected for sample-design effects following Jolliffe 

(2002/03) and are in parentheses. The second column under each of the poverty measures 

lists the percentage decline in the poverty index from the SNAP benefits. The estimated 

percent reduction is superscripted with *, **, or *** if the p-value is less than 0.1, 0.05, or 0.01, 

respectively. Standard errors for the percent decline are listed in parentheses and are secondorder approximations. Odd years only are listed due to space considerations; results in the 

even years are consistent with those presented for the odd years.

SNAP = Supplemental Nutrition Assistance Program.

Source: USDA, Economic Research Service calculations based on Current Population Survey 

Annual Social and Economic Supplement data.
15

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reveals that SNAP has a somewhat stronger effect on the depth and severity 

of poverty in nonmetropolitan than in metropolitan areas, which is consistent 

with the higher SNAP participation rates among households in nonmetropolitan versus metropolitan areas (Leftin, 2010). Table 7 reports the equivalent 

analysis for children, and again shows that the effect of SNAP at reducing 

the depth and severity of poverty is stronger among children than among 

the overall population in both metropolitan and nonmetropolitan areas. For 

example, SNAP benefits reduced the severity of poverty by an average of 

15.3 percent among the overall population in nonmetropolitan areas (table 

6, final row) and by an average of 22.5 percent among children in nonmetropolitan areas (table 7, final row). 

Table 7

Metro and nonmetro child poverty and SNAP benefits, 2001-09

Percentage reduction in child poverty from SNAP benefits

Year Area

Headcount Poverty gap Squared poverty gap

Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent

decline

2001 Metro 14.8 4.3 6.3 12.7*** 4.0 17.8***

(0.31) (2.83) (0.17) (3.18) (0.13) (3.67)

Nonmetro 19.6 3.4 8.5 12.9** 5.5 18.1**

(0.70) (4.81) (0.41) (5.88) (0.34) (7.02)

2003 Metro 16.3 4.5* 7.1 14.0*** 4.5 19.5***

(0.33) (2.67) (0.18) (3.02) (0.14) (3.49)

Nonmetro 19.3 4.3 7.7 16.0*** 4.7 22.7***

(0.67) (4.63) (0.33) (5.10) (0.26) (5.96)

2005 Metro 16.2 5.7** 6.9 15.6*** 4.3 21.5***

(0.33) (2.65) (0.17) (2.90) (0.13) (3.30)

Nonmetro 18.9 4.9 8.1 17.0*** 5.1 23.1***

(0.70) (4.93) (0.39) (5.54) (0.31) (6.50)

2007 Metro 16.2 5.7** 6.8 16.0*** 4.3 21.8***

(0.33) (2.69) (0.18) (2.99) (0.14) (3.48)

Nonmetro 21.0 5.2 8.7 16.3*** 5.5 22.0***

(0.75) (4.71) (0.40) (5.35) (0.32) (6.21)

2009 Metro 18.3 9.6*** 7.8 20.5*** 4.9 27.0***

(0.35) (2.34) (0.18) (2.55) (0.14) (2.91)

Nonmetro 21.1 10.4** 8.6 22.9*** 5.3 30.0***

(0.74) (4.29) (0.38) (4.68) (0.30) (5.34)

10 yr.

mean

Metro 16.1 5.5 6.8 15.2 4.3 21.0

Nonmetro 19.6 5.7 8.1 16.5 5.0 22.5

Note: All poverty indices are multiplied by 100. The first column under each of the three 

poverty indices lists the poverty estimates with SNAP benefits added to income. Standard 

errors for all poverty estimates are corrected for sample-design effects following Jolliffe 

(2002/03) and are in parentheses. The second column under each of the poverty measures 

lists the percentage decline in the poverty index from the SNAP benefits. The estimated 

percent reduction is superscripted with *, **, or *** if the p-value is less than 0.1, 0.05, or 0.01, 

respectively. Standard errors for the percent decline are listed in parentheses and are secondorder approximations. Odd years only are listed due to space considerations; results in the 

even years are consistent with those presented for the odd years.

SNAP = Supplemental Nutrition Assistance Program.

Source: USDA, Economic Research Service calculations based on Current Population Survey 

Annual Social and Economic Supplement data.
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SNAP’s Effect on Poverty Was Strongest in 2009

The findings summarized in tables 4 and 5 are displayed in figures 2 and 3, 

which plot the percent reduction due to SNAP benefits for each measure of 

poverty (fig. 2) and child poverty (fig. 3) by year.24 Figures 2 and 3 show that 

the percent decline is largest for the squared poverty gap, followed by the 

poverty-gap index, and both of these are significantly greater than the decline 

in the headcount index over all years considered. The figures also show that 

SNAP’s contribution to reducing poverty increased between 2000 and 2009, 

a period when the SNAP caseload nearly doubled and total SNAP benefits 

more than quadrupled. As noted previously, this time period was marked 

by two economic downturns and increasing State flexibility to determine 

program eligibility and simplify the program application process.

Figures 2 and 3 also make it clear that the effect of SNAP at reducing 

poverty and child poverty increased dramatically from 2008 to 2009, when 

additional SNAP benefits were authorized by the ARRA. Focusing on figure 

3, the antipoverty effect of SNAP increased most dramatically for the child 

headcount measure, by 55.6 percent between 2008 and 2009.25 In contrast, 

the antipoverty effect of SNAP increased by a more modest 20.8 percent for 

the poverty-gap index and by 18.5 percent for the squared-poverty-gap index.

The ARRA-authorized increase in the maximum SNAP benefit means that, 

for a given level of net income, a poor SNAP household could have a lower 

level of gross income and still be lifted over the poverty threshold by SNAP 

benefits.26 Because the SNAP benefit reduction rate was not changed, the 

dollar decrease in the minimum level of gross income that would allow 

24The corresponding figures for 

the metro and nonmetro areas show a 

similar relationship among the percent 

reductions in the headcount, povertygap, and squared-poverty-gap indices, 

and similar trends over time. 

25This is measured by the change in 

[(Pa - P ́a )/ Pa]*100 between 2008 and 

2009. For example, the percent decline 

in the child headcount resulting from 

SNAP benefits increased by 55.6 percent, from 6.3 in 2008 to 9.8 in 2009.

26Of course, the ARRA benefit 

increase would only decrease the prevalence of poverty among households 

whose pre-ARRA SNAP benefits would 

not have already lifted them above the 

poverty line.

Figure 2

Reduction in poverty from SNAP benefits, 2000-09 for all persons 

SNAP = Supplemental Nutrition Assistance Program.

Source: USDA, Economic Research Service calculations based on Current Population 

Survey Annual Social and Economic Supplement data.

Relative difference with SNAP benefits (percent)

2000 01 02 03 04 05 06 07 08 09

0

5

10

15

20

25

30

Rate: percent reduction with SNAP benefits

Depth: percent reduction with SNAP benefits

Severity: percent reduction with SNAP benefits
17

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SNAP benefits to lift a household out of poverty is the same for a given 

household size across a broad range of net income levels.27 Thus, the ARRA 

benefit increase would be expected to expand substantially the subset of poor 

households that received enough in SNAP benefits to lift them above the 

poverty threshold.

For example, among three-person families (whose poverty threshold is 

$1,440 per month) with net income between $0 and $1,306, monthly gross 

income could be $63 lower and SNAP benefits could still lift the family out 

of poverty.28 With net income between $1,306 and $1,396, the difference in 

the minimum gross income that would allow SNAP benefits to lift a threeperson family out of poverty decreases by 70 cents for each additional dollar 

in net income, since the distance between family net income and the poverty 

threshold is less than the post-ARRA SNAP benefit in this range. If net 

income is $1,396 or greater, the ARRA increase in benefits would not influence the prevalence of poverty, because pre-ARRA benefits would already 

have lifted the family out of poverty. In addition to increasing the subset of 

SNAP households who could be lifted above the poverty threshold by their 

SNAP benefits, the ARRA benefit increase may have also encouraged greater 

enrollment in SNAP among nonparticipating households in the income range 

that would be lifted above poverty by the increased benefit level.

27The exception is when the distance 

between net income and the poverty 

threshold is less than or equal to the 

SNAP benefit, in which case the constraint that gross income be greater than 

or equal to net income is binding.

28This example uses the poverty 

threshold for a family with one adult 

and two children, and assumes 12 

months of SNAP receipt.

Figure 3

Reduction in poverty from SNAP benefits, 2000-09 for all U.S. children 

SNAP = Supplemental Nutrition Assistance Program.

Source: USDA, Economic Research Service calculations based on Current Population 

Survey Annual Social and Economic Supplement data.

Relative difference with SNAP benefits (percent)

2000 01 02 03 04 05 06 07 08 09

0

5

10

15

20

25

30

Severity: percent reduction with SNAP benefits

Depth: percent reduction with SNAP benefits

Rate: percent reduction with SNAP benefits
18

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While the increase in the antipoverty effect of SNAP between 2008 and 

2009 was largest for the headcount measure, SNAP benefits were also quite 

effective at reducing the depth and severity of poverty in 2009. According 

to the measure of income used in the official poverty definition (shown in 

table 2), the depth of child poverty increased by 8.7 percent and the severity 

of child poverty increased by 7.9 percent from 2008 to 2009, as the severe 

economic downturn continued from 2007. However, table 5 shows that, after 

accounting for SNAP benefits, the increase from 2008 to 2009 in the depth 

of child poverty was only 3.9 percent and in the severity of child poverty 

was only 2.1 percent. While we did not estimate the exact contribution of 

the additional ARRA-authorized SNAP benefits, it is clear that total SNAP 

benefits in 2009 were quite successful in protecting the well-being of the 

poor during the 2007-09 recession.29 29For an evaluation of the effectiveness of overall 2009 ARRA spending 

on the headcount index, see Sherman 

(2011).
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Conclusions

Using data from the 2001 to 2010 March Supplement of the Current 

Population Survey, we show that the depth and severity of poverty, as well 

as the prevalence of poverty, were significantly higher for children than for 

the population in general and were higher for those in nonmetropolitan than 

for those in metropolitan areas. We then examined the effect on poverty of 

adding the value of SNAP benefits to family income. Our results showed 

that the prevalence of poverty, as measured by the headcount index, was 

not reduced much by SNAP. In contrast, the depth and severity of poverty, 

and particularly of child poverty, were significantly reduced by SNAP. The 

average decline from 2000 to 2009 in the child-poverty-gap index was 15.5 

percent, while the average decline in the squared-poverty-gap index for children was 21.3 percent. SNAP benefits reduced both the depth and severity 

of poverty in both metropolitan areas and nonmetropolitan areas, with somewhat greater poverty reductions among individuals in nonmetropolitan areas. 

The role of SNAP benefits in reducing the prevalence, depth, and severity of 

poverty increased steadily from 2000 to 2009, during a period of increasing 

State variation in program administration. Most of the program changes 

were designed to increase access to working poor households, who would be 

expected to be at the higher end of the income distribution among eligible 

households. While we did not find evidence that these program changes 

diminished the targeting effectiveness of the program, an important area of 

future research is to examine the influence of specific State SNAP policy 

choices, as well as changing macroeconomic conditions, on SNAP’s povertyreducing effect.30

The antipoverty effect of SNAP was highest in 2009, when the ARRA 

increased SNAP benefits to all participants, and SNAP benefits ensured that 

the depth and severity of poverty increased only slightly from their 2008 

levels despite worsening economic conditions. These results clearly show 

that an examination of only the headcount index, or prevalence of poverty, 

would lead to an understatement of the role of SNAP benefits in the reduction of poverty. Our analysis of the poverty-gap and squared-poverty-gap 

indices makes clear that SNAP plays an important role in improving the 

welfare of individuals in low-income households. 

30The role of economic conditions 

is of particular interest, in light 

of evidence that macroeconomic 

conditions in the 1980s and 1990s had a 

strong effect on poverty and its severity 

(Gundersen and Ziliak, 2004) and that 

SNAP participation has become more 

responsive to changes in unemployment 

since the 1996 welfare reform (Bitler 

and Hoynes, 2010).
20

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Appendix table 1

Poverty (130 percent)1 and SNAP benefits, 2000-09

Percentage reduction in poverty from SNAP benefits

Headcount Poverty gap Squared poverty gap

Year

Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent

decline

Income

+ SNAP

Percent

decline

2000 16.4 1.4 6.7 5.6*** 4.1 8.8***

(0.21) (1.81) (0.11) (2.13) (0.08) (2.57)

2001 16.8 1.0 7.1 5.6*** 4.4 8.7***

(0.17) (1.42) (0.09) (1.69) (0.07) (2.06)

2002 17.3 1.4 7.3 5.7*** 4.6 8.9***

(0.17) (1.37) (0.09) (1.62) (0.07) (1.93)

2003 17.7 1.3 7.6 6.4*** 4.8 9.8***

(0.18) (1.38) (0.09) (1.63) (0.07) (1.95)

2004 17.6 1.6 7.7 6.8*** 4.9 10.4***

(0.18) (1.39) (0.09) (1.62) (0.08) (1.93)

2005 17.7 1.6 7.6 7.1*** 4.9 10.8***

(0.17) (1.37) (0.09) (1.61) (0.07) (1.90)

2006 17.2 1.8 7.4 6.9*** 4.7 10.5***

(0.17) (1.40) (0.09) (1.64) (0.07) (1.97)

2007 17.6 1.8 7.4 7.2*** 4.7 10.9***

(0.18) (1.39) (0.09) (1.63) (0.07) (1.93)

2008 18.4 2.1 7.9 8.2*** 5.0 12.1***

(0.18) (1.35) (0.10) (1.56) (0.08) (1.85)

2009 19.1 2.9** 8.3 10.6*** 5.3 15.0***

(0.18) (1.30) (0.10) (1.47) (0.08) (1.71)

Mean:

2000-09 17.6 1.7 7.5 7.0 4.7 10.6

1This analyis uses a poverty threshold set at 130 percent of the Federal poverty threshold in 

each year. For example, a family of two adults and two children at 130 percent of the poverty 

threshold had an income of $28,283 in 2009.

SNAP = Supplemental Nutrition Assistance Program.

Note: All poverty indices are multiplied by 100. The first column under each of the three poverty 

indices lists the poverty estimates with SNAP benefits added to income. Standard errors for all 

poverty estimates are corrected for sample-design effects following Jolliffe (2002/03) and are 

in parentheses. The second column under each of the poverty measures lists the percentage 

decline in the poverty index from the SNAP benefits. The estimated percent reduction is superscripted with *, **, or *** if the p-value is less than 0.1, 0.05, or 0.01, respectively. Standard 

errors for the percent decline are listed in parentheses and are second-order approximations.

Source: USDA, Economic Research Service calculations based on Current Population Survey 

Annual Social and Economic Supplement data