Regional workshop on the Production of Population Estimates
and Demographic Indicators
Addis Ababa, 5-9 October
Evaluation and Analysis
of Age and Sex Structure
François Pelletier & Thomas Spoorenberg
Population Estimates and Projections Section
Evaluation method of age and sex distribution data
Basic graphical tools
o Graphical analysis
• Population pyramids
• Graphical cohort analysis
o Age and sex ratios
o Summary indices of error in age-sex data
• Whipple’s index
• Myers’ Blended Method
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Importance of age-sex structure
Planning purposes – health services, education
programs, transportation, labour supply
Social science, economist, gender studies
Studying population dynamics – fertility, mortality,
migration
Insight on quality of census enumeration
Having strong effect on other characteristics of a
population
o Determined by fertility, mortality and migration, and follows
fairly recognizable patterns
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
What to look for at the evaluation
Possible data errors in the age-sex structure, including
o Age misreporting (age heaping and/or age exaggeration)
o Coverage errors – net underenumeration (by age or sex)
Significant discrepancies in age-sex structure due to extraordinary
events
o High migration, war, famine, HIV/AIDS epidemic etc.
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Approaches to collecting age and its impact on quality
Age - the interval of time between the date of birth and the date of
the census, expressed in completed solar years
Two approaches
o The date of birth (year, month and day) - more precise information and is preferred
o Completed age (age at the individual’s last birthday) – less accurate
• Misunderstanding: the last, the next or the nearest birthday?
• Rounding to nearest age ending in 0 or 5 (age heaping)
• Children under 1 may be reported as 1 year of age
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Basic graphical methods – Population Pyramid
Basic procedure for assessing the quality of census data on age and
sex
Displays the size of population enumerated in each age group (or
cohort) by sex
The base of the pyramid is mainly determined by the level of fertility
in the population, while how fast it converges to peak is determined
by previous levels of mortality and fertility
The levels of migration by age and sex also affect the shape of the
pyramid
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – France, 1954 (Source: Pison 2014)
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – France, 1974 (Source: Pison 2014)
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – France, 2014 (Source: Pison 2014)
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – High population growth
Age
95+
90 MALE
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
50,000
Central African Republic, 1988 Census
FEMALE
Wide base, triangle-shaped
pyramid indicates high fertility
25,000
0
Population
25,000
50,000
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – Low population growth
Age
“baby boom”
Italy, 2011 Census
95+
90 MALE
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
500,000
FEMALE
1940-45 Birth deficit
due to WWII
Flattening and narrowing base
Indicates long-term low fertility
300,000
100,000
100,000
Population
300,000
500,000
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – Detecting errors
Age
85+
80
MALE
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
320,000 220,000
YEMEN, 1975 Census
FEMALE
Age
85+
80-84
75-79
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
5-9
0-4
YEMEN, 1975 Census
MALE
1,500,000
FEMALE
750,000 Population
0
750,000
1,500,000
Age misreporting errors (heaping) among adults
Under enumeration of young children (< age 2)
High fertility level
120,000
20,000 80,000
Population
180,000
280,000
Smaller population in 20-24 age group
>> extraordinary events in 1950-55?
Less men relative to women in 20-44 age group
>> labor out-migration?
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – Detecting errors
Age
TUNISIA, 1966 Census
100+
95
FEMALE
90 MALE
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
100,00075,000 50,000 25,000 0 25,000 50,000 75,000100,000
Population
Age heaping
Age
TUNISIA, 1994 Census
100+
95
FEMALE
90 MALE
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
120,00090,000 60,000 30,000 0 30,000 60,000 90,000120,000
Population
Declining fertility
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – Detecting errors
Age
85+
80
MALE
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
30,000 20,000
Age
Bahrain, 2010 Census
FEMALE
80-84
U.A.E., 2005 Census
MALE
FEMALE
70-74
60-64
50-54
40-44
30-34
20-24
10-14
0-4
10,000
0
10,000
Population
20,000
30,000
500,000
300,000
100,000 100,000
Population
!!! Effect of Labor migration !!!
>> Importance of knowledge of the context
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
300,000
500,000
Population pyramid – Line instead of bars
Population Pyramid (bar chart)
>> Not always easy to determine differences by sex
Use of line chart
Bangladesh, 2001 Census
Male
Female
Population
3,000,000
Age
Bangladesh, 2001 Census
85+
80
FEMALE 2,500,000
75 MALE
70
65
2,000,000
60
55
50
1,500,000
45
40
35
30
1,000,000
25
20
15
500,000
10
5
0
0
3,000,000 1,500,000
0
1,500,000 3,000,000
Population
0
5
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80+
Age
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Population pyramid – Line instead of bars
Bangladesh, 2001 Census
Bangladesh, 2001 Census
9,000,000
3,000,000
2,500,000
Male
8,000,000
Male
Female
7,000,000
Female
6,000,000
Population
Population
2,000,000
1,500,000
5,000,000
4,000,000
3,000,000
1,000,000
2,000,000
1,000,000
500,000
0
0
0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80+
Age
Age group
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Basic graphical methods – Graphical cohort analysis
Tracking actual cohorts over multiple censuses
The size of each cohort should decline over each census due to
mortality (with no significant international migration)
The age structure (the lines) for censuses should follow the same
pattern in the absence of census errors
An important advantage >> possible to evaluate the effects of
extraordinary events and other distorting factors by following actual
cohorts over time
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Graphical cohort analysis – Example (1)
Mozambique, 1997 and 2007 Censuses
0-4
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85-89
90-94
1997 Census
Male
Female
1,353,206
1,388,350
1,112,321
1,113,675
947,236
878,429
774,327
854,078
637,113
827,614
509,109
654,465
410,148
477,562
373,813
428,395
270,046
303,147
257,070
282,098
178,902
212,060
162,122
174,234
114,335
125,096
100,425
109,288
47,407
50,607
41,529
42,858
15,305
17,326
2007 Census
Male
Female
1,222,668
925,729
774,413
707,603
583,689
481,396
366,518
321,236
231,232
194,011
140,146
113,840
72,288
55,448
22,417
16,576
4,803
1,183,939
991,323
986,526
841,416
667,865
556,191
389,087
328,660
283,288
208,657
159,557
127,794
81,329
61,012
28,278
19,448
5,883
Birth Cohort
2002-2007
1997-2001
1992-1997
1987-1992
1982-1997
1977-1982
1972-1977
1967-1972
1962-1967
1957-1962
1952-1957
1947-1952
1942-1947
1937-1942
1932-1937
1927-1932
1922-1927
1917-1922
1912-1917
Data is organized by birth
cohort
Exclude open-ended age
category
People who were born in
the same years are
compared in the analysis
Source: United Nations Statistics Division,
Demographic Yearbook Statistical
Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Graphical cohort analysis – Example (1)
Mozambique, 1997 and 2007 Censuses
1,600,000
1,600,000
MALE
1,400,000
Male - 1997 Census
1,200,000
FEMALE
1,400,000
Female - 1997 Census
1,200,000
Male - 2007 Census
Female - 2007 Census
Population
1,000,000
800,000
800,000
600,000
400,000
400,000
200,000
200,000
0
0
1992-1997
1987-1992
1982-1997
1977-1982
1972-1977
1967-1972
1962-1967
1957-1962
1952-1957
1947-1952
1942-1947
1937-1942
1932-1937
1927-1932
1922-1927
1917-1922
1912-1917
1907-1912
600,000
1992-1997
1987-1992
1982-1997
1977-1982
1972-1977
1967-1972
1962-1967
1957-1962
1952-1957
1947-1952
1942-1947
1937-1942
1932-1937
1927-1932
1922-1927
1917-1922
1912-1917
1907-1912
Population
1,000,000
Birth cohort
Birth cohort
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Graphical cohort analysis – Example (2)
Republic of Korea, 2000 and 2010 Censuses, Men
2,500,000
Male - 2000 Census
Population
2,000,000
Male - 2010 Census
1,500,000
1,000,000
500,000
0
Birth cohort
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Graphical cohort analysis – Example (2)
Republic of Korea, 2000 and 2010 Censuses, Women
2,500,000
Female - 2000 Census
Female - 2010 Census
Population
2,000,000
1,500,000
1,000,000
500,000
0
Birth cohort
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Age ratios (1)
In the absence of sharp changes in fertility or mortality, significant
levels of migration or other distorting factors, the enumerated size
of a particular cohort should be approximately equal to the average
size of the immediately preceding and following cohorts
The age ratio for a particular cohort to the average of the counts for
the adjacent cohorts should be approximately equal to 1 (or 100 if
multiplied by a constant of 100)
Significant departures from this “expected” ratio indicate either the
presence of census error in the census enumeration or of other
factors
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Age ratios (2)
Age ratio for the age category x to x+4
2∗
5
= The age ratio for the age group to
4
= The enumerated population in the age category to
4
= The enumerated population in the adjacent lower age category
= The enumerated population in the adjacent higher age category
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Age ratios (3) – example
Mozambique – 1997 Census
1.2
1.2
1
1
0.8
0.6
0.4
0.8
0.6
0.4
Male
0.2
Mozambique – 2007 Census
1.4
Age ratio
Age ratio
1.4
0.2
Female
Male
Female
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
80-84
85-89
0
5-9
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74
75-79
0
Age group
Age group
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Sex ratios (1) - calculation
Sex ratio by age group
or
Sex Ratio =
Sex Ratio =
∙ 100
Where
= Male population enumerated in a specific age group
= Female population enumerated in the same age group
Value of sex ratio
Interpretation
1
Same number of men and women in a given age group
Above 1
More men than women in a given age group
Below 1
Less men than women in a given age group
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Sex ratios – Example (Expected sex ratio by age)
Sweden, selected years 1950-2015
110
Sex ratio (Number of men per 100 women)
100
90
80
70
60
50
40
30
1950
1975
20
10
2000
2015
0
Age group
Source: United Nations Population Division, The World Population Prospects: The 2015 Revision
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Sex ratios – Example
Mozambique, 1997 and 2007 Censuses
Sex ratio (number of men per 100 women)
140
1997 Census
120
2007 Census
100
80
60
40
20
Rather sex ratio:
> Under-enumeration
of boys?
> Higher male child
mortality?
No decline at adult and older ages:
> Higher female mortality?
> Higher female out-migration?
> Under-enumeration of adult and older women?
>…
0
Age group
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Sex ratios – Cohort analysis
Sex ratio (number of men per 100 women)
Republic of Korea, 2000 and 2010 Censuses
120
> Excess of men in
1975-1980 birth
cohort in 2000
census only
100
80
60
> Other age groups:
as expected
40
2000 Census
20
2010 Census
0
Birth cohort
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Sex ratios – Cohort analysis
Sex ratio (Number of men per 100 women)
Mozambique, 1997 and 2007 Censuses
120
100
> Very different
patterns found in
each census
80
60
> Some consistencies
for birth cohorts
1947-1952 to 19271932
40
20
1997 Census
2007 Census
0
Birth cohort
Source: United Nations Statistics Division, Demographic Yearbook Statistical Database
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Summary indices – Whipple’s Index
Developed to reflect preference for or avoidance of a particular terminal digit
(or of each terminal digit)
If heaping on terminal digits “0” and “5” is measured:
… #
∙
$
… !#
!
!
"
"
∙ 100
W ranges between 100, representing no preference for “0” or “5” and 500,
indicating that only digits “0” and “5” were reported
W is usually computed on the age range 23 to 62
>> childhood and older ages are often excluded because they are more strongly affected by
other types of errors of reporting than by preference for specific terminal digits
Source: Shryock and Siegel (1980)
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Whipple’s Index (3)
The index can be summarized through the following categories:
Value of Whipple’s index (W)
Interpretation
<= 105
Highly accurate data
105 – 109.9
Fairly accurate data
110 – 124.9
Approximate data
125 – 174.9
Rough data
>= 175
Very rough data
>> these values must be interpreted keeping in mind the past and present context
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Whipple’s index around the world (most recent census, 1985-2003)
Source: UN Demographic Yearbook special issue on age heaping: http://unstats.un.org/unsd/demographic/products/dyb/dybcens.htm
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Improvement in the accuracy of age reporting over time
Whipple’s Index, Turkey 1950-2000
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Summary indices – Myers` Blended Index
It is conceptually similar to Whipple’s index, except that the index
considers preference (or avoidance) of age ending in each of the
digits 0 to 9 in deriving overall age accuracy score
The theoretical range of Myers’ Index is from 0 to 90, where 0
indicates no age heaping and 90 indicates the extreme case where
all recorded ages end in the same digit
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Conclusion: Uses and limitations
Assessment of the age and sex structure of a population
enumerated is typically the first step taken in evaluating a data
collection operation by means of demographic methods
Demographic methods provide:
• A quick and inexpensive indication of the general quality of data
• Evidence on the specific segments of the population in which the presence of
error is likely
• “Historical” information which may be useful for interpreting the results of
evaluation studies based on other methods, and in determining how the
collected data should be adjusted for use in demographic analyses
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
Conclusion: Uses and limitations
The major limitation of age and sex structure analysis is that it is
not possible to derive separate numerical estimates of the
magnitude of coverage and content error on the basis of such
analyses alone
It is often possible to assess particular types of errors which are
likely to have affected the population counts for particular
segments of the population. Estimates of coverage error from other
sources often are required to verify these observations
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015
References
Pison, G. (2014), “1914-2014 : A century of change in the French population pyramid”, Population & Societies
No. 509 (March 2014)
Shryock, H. S. and Siegel, J. S. (1980), The Methods and Materials of Demography, Washington, D.C.: U.S.
Government Printing Office.
Moultrie T.A., R.E. Dorrington, A.G. Hill, K. Hill, I.M. Timæus and B. Zaba (eds), (2013), Tools for Demographic
Estimation, Paris: International Union for the Scientific Study of Population, available online at:
http://demographicestimation.iussp.org/
U.S. Census Bureau (n.d.), Population Analysis System (PAS), Washington, D.C., U.S. Census Bureau,
available online at: http://www.census.gov/population/international/software/uscbtoolsdownload.html
Regional Workshop on the Production of Population Estimates and Demographic Indicators
Addis Ababa, 5-9 October 2015