Measurement of Poverty:
Concepts & Measurements
Measurement of Poverty
1
Measurement of Poverty
“The governments are very keen on
amassing statistics. They collect them,
add them, raise them to the nth power
and take the cubed root and prepare
wonderful diagrams.
But you must never forget that every
one of these figures comes in the first
instance from the village watchman who
just puts down whatever he damn well
pleases.”
- Sir Josiah Stamp
Measurement of Poverty
2
Measurement of Poverty Practical
Concerns
• Identification of Poverty Line
• Defining the Unit of Measurement
• Selecting the Indicator of Well-being
Measurement of Poverty
3
Identification of Poverty Lines
• The point at which the poor are separated
from the non-poor
– Relative Poverty Lines
– Absolute Poverty Lines
Measurement of Poverty
4
Absolute Poverty Lines
Type
Food Energy Intake
Cost of Basic Needs
World Bank US$1 /
day
Description
 Based on observed
relation between
calorie intake and
total household
expenditure
 Identifies bundle of
goods necessary to
meet basic needs,
then estimates cost
 US$370 / year
Features
 PL may vary by subgroups of population
e.g. by region
 Most common
method
 Identification of
basic needs may not
be strghtfwd
 Eases comparison
across countries
 Zero cost of
calculation
 Conversion to local
currency problematic
Measurement of Poverty
5
Food Energy Intake Method
• Sets PL at the level of expenditure at which FEI is
just sufficient to meet basic nutrition requirements
• STEP ONE: Establish the minimum nutrition
requirements.
• STEP TWO: Examine the observed spending pattern
to see at what average expenditure household just
achieve minimum nutrition requirement.
Measurement of Poverty
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Food Energy Intake Method
Food
Energy
Intake
Min Nutrition
Standard (eg 2100
cals.)
PL
Measurement of Poverty
Expenditure
(or Income)
7
Food Energy Intake Method
• The PL determined by the FEI method may
vary across regions due to differences in:
Preferences: if more expensive animal protein and
less food grain is eaten.
Relative Prices: in urban areas it may cost more to
obtain basic nutrition because food prices are higher.
Publicly Provided Goods: in capital city transport
to/from work may be cheaper than in provincial cities,
allowing for lower expenditure level to meet
minimum FEI.
Measurement of Poverty
8
Food Energy Intake Method
• This method does take account of non-food
purchases.
Measurement of Poverty
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Cost of Basic Needs
• PL is equal to the value of a bundle of
consumption goods necessary to meet basic
needs
May include just food (extreme poverty)
But more commonly includes non-food items
Measurement of Poverty
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Cost of Basic Needs
• STEP ONE: Establish the minimum
consumption bundle necessary to meet basic
needs
Measurement of Poverty
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Cost of Basic Needs
• STEP TWO: Establish the cost for the items in
the basic consumption bundle
Measurement of Poverty
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Additional Considerations in Setting
Poverty Lines
• Regional Poverty Lines
Significant regional price differences may exist
Urban / Rural poverty lines common
• Sensitivity Analysis
Typically near mode of distribution
Multiple poverty lines often tried
Measurement of Poverty
13
Distribution of Expenditure
Mexico, 1992
0.18
Poverty Line
0.14
0.12
0.1
0.08
0.06
0.04
0.02
10600
10100
96000
91000
86000
81000
76000
71000
66000
61000
56000
51000
46000
41000
36000
31000
26000
21000
16000
11000
6000
0
1000
Population Share
0.16
Expenditure/Quarter (1984 pesos)
Measurement of Poverty
14
10
00
60
00
11
00
0
16
00
0
21
00
0
26
00
0
31
00
0
36
00
0
41
00
0
46
00
0
51
00
0
56
00
0
61
00
0
66
00
0
71
00
0
76
00
0
81
00
0
86
00
0
91
00
0
96
00
10 0
10
0
10 0
60
00
Cumulative Percentage of Population
Cumulative Distribution of
Expenditure
Mexico, 1992
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Poverty Line
0
Expenditure/Quarter (1984 pesos)
Measurement of Poverty
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Measurement of Poverty Practical
Concerns
• Identification of Poverty Line
• Defining the Unit of Measurement
• Selecting the Indicator of Well-being
Measurement of Poverty
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Defining the Unit of Measurement
Household vs. Individual
Adjusting for differences among HH
Adjusting for the age / gender of HH members
Adjusting for HH size
Measurement of Poverty
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Defining the Unit of Measurement
• Example:
2 HH with monthly Y of $150
HH1 has 2 members…per capita Y = $75
HH2 has 3 members …per capita Y = $50
BUT:
• HH1 has 2 adult men
• HH2 has woman and 2 small children
Measurement of Poverty
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Equivalence Scales and Economies of
Scale
• HH size is often measured in “adult
equivalent” units
each member of the HH counts as some fraction
of an adult male
Economies of scales can then be accounted for by
scaling the adult equivalent units
Measurement of Poverty
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Equivalence Scales and Economies of
Scale
• Many different methodologies are followed
within two basic approaches
Fixed Scales
Estimated Scales
Measurement of Poverty
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Fixed Scales
• Ex 1: Adult Equivalent Scale:
Adult Male = 1
Adult Female = 0.74
Child < 5 years = 0.6
• Ex 2: OECD Scale: AE=1+0.7*(A-1)+0.5*C
– First adult = 1
– Additional adults = 0.7
– Children < 14 = 0.5
Measurement of Poverty
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Estimating AE Scales
• Based on examining HH data to see how
consumption varies with gender/age and size
Food share of expenditure is regressed on HH
size, HH composition
Measurement of Poverty
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Examples of AE Estimated Scales
• Ex 1: Deaton and Meullbauer, Sri Lanka,
Indonesia
Adults = 1
Child 13-17 = 0.5
Child 7-12 = 0.3
Child < 7 = 0.2
Measurement of Poverty
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Examples of AE Estimated Scales
• Ex 2: Deaton, India and Pakistan
– The AE value of adding another person to a HH
with 2 adults:
Age 0-4 = 0.48
Age 5-9 = 0.56
Age 10-14 = 0.60
Age 15-54 = 0.68
Measurement of Poverty
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What is a HH?
• UN definition:
– “Group of people who eat together”
• But: how long must one be a resident to be counted as
part of a HH
– Students, migrant workers, etc.
Measurement of Poverty
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Measurement of Poverty Practical
Concerns
• Identification of Poverty Line
• Defining the Unit of Measurement
• Selecting the Indicator of Well-being
Measurement of Poverty
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Selecting the Indicator of
Well-being
• Monetary Measure of Welfare
Income
Expenditure
• Non-Monetary Measures of Welfare
Direct Measures
Subjective Measures
Measurement of Poverty
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Income
• Definition: Y = C +  in net worth
• Example
Assets start of year: $10K
Spending on consumption: $3K
Assets end of year: $11K
Annual Y: $4K
Measurement of Poverty
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Problems with Income as Welfare
Measure
• Conceptual Problems
– Goal is to measure HH ability to meet basic
needs, but Y is just one factor
• access to credit, public services, access, etc. are other
factors that determine ability to meet basic needs
Measurement of Poverty
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Problems with Income as Welfare
Measure
• Measurement Problems
– Understating of Y
Difficult to recall all of Y, especially when Y flow is
erratic as in the informal sector
Fear of tax collector
Illegally earned Y
Separating inputs from revenue in agriculture
Accounting for own consumption of output
Measurement of Poverty
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Expenditure
• Generally preferred to Income
– Is more direct measure of what is consumed
– Less volatile than Y
• Consumption smoothing...
Measurement of Poverty
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Consumption Smoothing
Income
Consumption
Y
C
Time
Measurement of Poverty
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Calculating Y or Expenditure
for HH
• How do we measure Y / Expenditure?
• What is included?
• NB: HH may be both producers and
consumers
Measurement of Poverty
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Measuring Y and Expenditure
HH as Consumer
Household
Expenditure
Household Y






Wage Y
Agricultural Y
Non-farm self-employment
Rent and Imputed Rent
Net inter-HH transfers
Other Y




Food expenditure
C of own-produced food
Housing expenditure
Non-food expenditure
Measurement of Poverty
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Measuring Y and Expenditure
Household as Producer
Receipts
Outgoing
 Revenue from sale of output
 Own-consumption for
produced output
 Cash expenditure on inputs
 In-kind expenditure on inputs
Measurement of Poverty
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Calculating Y and Expenditure
• Must not include:
Inputs into HH production, like money spent on
seeds, fertilizer
Expenditure on investment, like purchase of tools
Measurement of Poverty
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Calculating Y and Expenditure
• Should include:
Housing for owner-occupied dwellings
Expenditure on durable goods
Measurement of Poverty
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Non-Monetary Measure
of Welfare
• Direct Welfare Measures
Nutrition Poverty
Health Poverty
Education Poverty
Measurement of Poverty
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Nutrition Poverty
• Input
– Example: Calories per day
• Outcomes
– Example: Malnutrition
Measurement of Poverty
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Health Poverty
• Outcomes
– Ex: life expectancy, infection rates
• Inputs
– Ex: vaccination rates
Measurement of Poverty
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Education Poverty
• Outcomes
– Ex: Literacy rates
• Inputs:
– Ex: Enrolment numbers
Measurement of Poverty
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Subjective Measures
• HH may be asked directly about their welfare
• HH may be asked to establish minimum
standards
• Community indicators may be established
Measurement of Poverty
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Poverty Measures
• We may want to measure poverty directly
instead of looking at Y and inequality
together
• The most commonly used poverty measures
are:
Head Count Index
Poverty Gap
Proportional Poverty Gap
Squared Poverty Gap
Measurement of Poverty
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Head Count Index
• HCI = (# poor) / (population)
• Measures the “incidence” of poverty
– i.e. it tells us “How many poor”
Measurement of Poverty
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Head Count Index
• Simplest and most commonly used measure
• Limitations:
Does not account for depth of poverty; i.e. it
does not tell us how far below the poverty line
the poor are.
• Advantages:
Simple to understand, straightforward
interpretation.
Additive across populations.
Measurement of Poverty
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Regional Head Count Estimates
Extreme Poverty <$275/year
SSA:
South Asia:
ME/NA:
LA / Car:
East Asia:
HC
.30
.29
.21
.12
.09
Measurement of Poverty
Millions of
People
120
300
40
50
120
46
Regional Head Count Estimates
Moderate Poverty < $370/year
SSA:
South Asia:
ME/NA:
LA / Car:
East Asia:
HC
.48
.52
.31
.22
.13
Measurement of Poverty
Millions of
People
184
532
60
87
182
47
Absolute Poverty Gap
• PG = (# Poor) * (Y shortfall)
• PG = (Z-Yi) ;
– where Z is PL, Yi is income of person i
• It tells us the total Y shortfall of the poor; i.e.
the absolute amount that would be needed
to raise all the poor up to the poverty line.
Measurement of Poverty
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Absolute Poverty Gap
Poverty Gap
Y
PL
Population
(poorest to richest)
Measurement of Poverty
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Absolute Poverty Gap
Y
Y
Poverty
Gap
PL
PL
Population
Relatively large
poverty gap
Population
Relatively small
poverty gap
Measurement of Poverty
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Proportional Poverty Gap
• PPG = (1/N){(Z-Yi)/Z}
• Measures the “depth” of poverty
• It gives some weight to how far below the
poverty line a poor individual is
– If a poor person’s income fall, the HC won’t
change, but the PPG will increase to reflect the
increase in the depth of poverty
Measurement of Poverty
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Squared Poverty Gap(Foster-Greere
Thorbecke)
• PPG = (1/N){(Z-Yi)/Z}2
• Measures the “severity” of poverty
• Squares the difference between the poverty
line and each household’s income
– provides much greater weight to the poorest of
the poor because the farther the HH from the
poverty line, the greater the weight it is given
Measurement of Poverty
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Poverty Measures
• Head Count
• Proportional Poverty
Gap
• Squared Poverty Gap
• Absolute Poverty Gap
• Income Distribution
Y
PL
Pop (poorest to richest)
Measurement of Poverty
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Poverty Measures
• These first 3 poverty measures are often
referred to as the Foster-Greere-Thorbecke
family of indices
• They can all be written as:
– Pα= (1/N){(Z-Yi)/Z}
• =0 is HC
• =1 is PPG
• =2 is SPG
Measurement of Poverty
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Poverty Measures from Mexico
1984
Rural
Urban
1989
Rural
Urban
HC
PPG
SPG
.90
.72
.58
.35
.42
.21
.94
.68
.62
.32
.61
.39
Measurement of Poverty
55
Human Development Index
• An attempt to account for some of the
limitations of using just income or
expenditure as a measure of welfare
• Tries to take seriously some of Sen’s
arguments about capabilities
– Sen argues that the goal is to increase
capabilities …to be well fed, educated, healthy
– These capabilities won’t always be perfectly
correlated with income
Measurement of Poverty
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Income and Capabilities
Sri Lanka
Per Capita
Share of
Share of
Income
Poorest 40% Richest 20%
2,990
22
39
Guatemala
3,350
8
63
Sri Lanka
Life
Expectancy
72
Infant
Mortality
18
Adult
Literacy
89
Guatemala
65
48
54
Measurement of Poverty
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HDI
• Consists of 3 elements
• Life Expectancy
– Educational Attainment
2/3 Adult Literacy
1/3 School Enrolment
– Per Capita Income
Adjusted down for Y > $5K
• Each component scored on 0 - 1 scale
• Index is simple average of 3 components
Measurement of Poverty
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Gender Development Index
• Motivated by inequality in the distribution of
resources across gender.
• Is there evidence that resources are
distributed unequally?
• The same 3 components as HDI, but gives
weight to relative equality in Y and
achievement of capabilities by gender.
Measurement of Poverty
59
Human Poverty Index
• Attempt by UNDP to take Sen’s capability
approach even more seriously
• Index combines 3 parts:
Vulnerability to early death
Access to education
Overall standard of living
• Health, water, nutrition
Measurement of Poverty
60
Measurement of Poverty
The secret of truth
is that there are no facts,
only stories.
- Joao Ubaldo Ribeira
Brazilian novelist
Measurement of Poverty
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