Moving to the Median and Expanding the Estimation 

Sample: The Case for Changing the Expenditures 

Underlying SPM Thresholds

Liana E. Fox

U.S. Census Bureau

Thesia I. Garner

Bureau of Labor Statistics

May 20, 2019

The views expressed in this research, including those related to statistical, methodological, 

technical, or operational issues, are solely those of the author and do not necessarily reflect the 

official positions or policies of the U.S. Census Bureau or Bureau of Labor Statistics. The author 

accepts responsibility for all errors. This presentation is released to inform interested parties of 

ongoing research and to encourage discussion of work in progress. This presentation reports the 

results of research and analysis undertaken by U.S. Census Bureau and Bureau of Labor Statistics 

staff. It has undergone more limited review than official publications. This presentation meets all 

of the U.S. Census Bureau’s Disclosure Review Board (DRB) standards and has been assigned DRB 

approval number CBDRB-FY19-ROSS-B0099. Do not cite or distribute without author permission.
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How to Determine Poverty Status

• All resource unit members have the same poverty status. 

• For individuals who do not live with family members, their individual resources 

are compared with the appropriate threshold. 

Resources Needs

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Which Goods and Services? 

Food, Clothing, Shelter, Utilities (FCSU)

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+ multiplier for other basic goods and services
Based on Whom?

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ITWG-5 years

NAS-3 years

NAS- CUs with 

2 adults and 2 

children

ITWG-CUs with 2 

children

Standards of living

Estimation

sample

Represented by

ITWG- 33rd

percentile 

FCSU

NAS-78%-83% of 

median FCSU
Current SPM Threshold Construction

• Produced by Bureau of Labor Statistics-Division of Price and Index Number Research 

(BLS-DPINR) using 5 years of Consumer Expenditure Survey Interview (CE) data

• 30th-36th percentile of expenditures of food, clothing, shelter, and utilities (FCSU) plus 

additional 20% 

• Based on estimation sample of resource units with exactly 2 kids

• Separate thresholds by housing tenure: Owners with mortgage, owners without 

mortgage and renters

• Adjust for unit size/composition and geography

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Changes Under Consideration

Expand estimation sample from CU’s with exactly 2 children

• Increase sample size

• Reflect spending patterns of a larger share of the population

Move base from 30-36th percentile to median of FCSU dist.

• Reduce impact of imputed benefits

• Allow for future incorporation of medical expenses

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Expand Estimation Sample

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• Increase sample size

• Reflect spending patterns of a larger share of the population

Source: Bureau of Labor Statistics, Consumer Expenditure Survey 

Interview Data, 2012Q2-2017Q1.
Sample Size for Estimation Samples

CU's with 2 

kids CU's with 1+ kids All CU's

Total Estimation Sample 

(unweighted) n = 14,668 n = 40,620 n = 129,604

30-36th ptile FCSU n=860 n=2,396 n= 7,632

Owners with mortgage 305 773 1,730

Owners without mortgage 112 332 2,646

Renters 443 1,291 3,256

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Source: Bureau of Labor Statistics, Consumer Expenditure Survey Interview Data, 2012Q2-2017Q1.
Change Base of Thresholds 

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1 33 50 100

Percentile of the FCSU Distribution

Move base to median

• Reduce impact of imputed benefits

• Allow for future incorporation of medical expenses
Share of CUs Receiving Benefits

30-36th Ptile of FCSU 47-53rd Ptile of FCSU

Public Housing 2.4 1.4

Govt. Asst. with Rent 2.0 1.4

SNAP 21.9 12.5

Private Health 

Insurance

65.2 74.3

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Note: Estimation sample is consumer units with exactly two children.

Source: Bureau of Labor Statistics, Consumer Expenditure Survey Interview Data, 2012Q2-2017Q1.
Alternative Thresholds Examined

• 80% of 47th-53rd percentile (Median)

• CU’s with 1+ kids

• All CU’s

CU’s with 2 kids CU’s with 1+ kid All CU’s

30th-36th ptile 33rd/2 kids 33rd/1+ kids 33rd/All

80% of 47th-53rd

ptile 50th/2 kids 50th/1+ kids 50th/All

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Threshold Values Relative to 33rd/2 kids

CU’s with 2 kids CU’s with 1+ 

kid All CU’s

30th-

36th

Owners with mortgages

Owners without mortgages

Renters

$26,336

$22,298

$26,104

$25,530

$21,807

$25,412

$27,463

$24,441

$27,235

80% of 

47th-

53rd

Owners with mortgages

Owners without mortgages

Renters

$26,103

$21,859

$25,439

$25,111

$21,225

$24,901

$27,664

$24,408

$27,542

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Source: Bureau of Labor Statistics, Consumer Expenditure Survey Interview Data, 2012Q2-2017Q1.
2016 SPM Rates

CU’s with 2 kids CU’s with 1+ kid All CU’s

30th-36th ptile 13.97 13.28 15.37

80% of 47th-53rd

ptile 13.45 12.79 15.58

• Rates follow same pattern as thresholds

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Source: U.S. Census Bureau, Current Population Survey, 2017 Annual Social and Economic Supplement.
Change in SPM Rates from 2011-2016

CU’s with 2 kids CU’s with 1+ kid All CU’s

30th-36th ptile -2.11 -1.54* -1.81

80% of 47th-53rd

ptile -1.90 -1.58 -1.76

• Only 33rd/1+ kid statistically different from 33rd/2 kids

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Source: U.S. Census Bureau, Current Population Survey, 2017 Annual Social and Economic Supplement.
SPM Rates by Age: 2016

33rd/2 kids 50th/All CU’s Difference 

Overall 13.97

(0.25)

15.58

(0.25) 1.61*

Under 18 15.24

(0.47)

17.24

(0.48) 2.01*

18 to 64 years 13.35

(0.29)

14.74

(0.28) 1.39*

65 years and older 14.55

(0.47)

16.43

(0.50) 1.88*

* An asterisk following an estimate indicates difference is statistically different from zero at the 90 

percent confidence interval. Note: Margins of error in parentheses. Source: U.S. Census Bureau, 

Current Population Survey, 2017 Annual Social and Economic Supplement.

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Summary/Recommendations

• We recommend expanding the estimation sample

• 1+ kids would nearly triple sample size, and keep similar attributes.

• All CU’s would increase sample size 9-fold, but concern that families without 

children spend differently than families with children.

• We recommend moving the base of the threshold from 33rd to some 

percentage of median.

• In 2016, 75.5% of median would match 33rd/2 kids overall SPM rate.

• In 2011, 77% of median would match 33rd/2 kids overall SPM rate.

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Contact

Liana E. Fox

Social, Economic & Housing Division

U.S. Census Bureau

liana.e.fox@census.gov

Thesia I. Garner

Division of Price and Index Number Research

Bureau of Labor Statistics

Garner.Thesia@bls.gov

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Extra Slides

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ITWG Guidance

• According to the ITWG recommendations, SPM should be seen as a 

research measure, improving due to changes in data, methodology or 

research.

• Priority should be placed on “consistency between threshold and 

resource definitions, data availability, simplicity in estimation, stability 

of the measure over time, and ease in explaining methodology (ITWG, 

2010).”

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Source: U.S. Census Bureau, Current Population Survey, 2017 Annual Social and 

Economic Supplement. www2.census.gov/library/publications/2017/demo/p60-

261.html. 

Supplemental Poverty Measure (SPM)

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