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 Central African Republic, 1988 Census 95+ 90 MALE FEMALE 85 80 75 70 65 60 55 50 45 40 35 30 25 20 Wide base, triangle-shaped 15 pyramid indicates high fertility 10 5 0 50,000 25,000 0 25,000 50,000 Population 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 Italy, 2011 Census 95+ 90 MALE FEMALE 85 80 75 70 1940-45 Birth deficit 65 due to WWII 60 “baby boom” 55 50 45 40 35 30 25 20 15 Flattening and narrowing base 10 Indicates long-term low fertility 5 0 500,000 300,000 100,000 100,000 300,000 500,000 Population
Regional Workshop on the Production of Population Estimates and Demographic Indicators Addis Ababa, 5-9 October 2015 Age YEMEN, 1975 Census Population pyramid – Detecting errors 85+ 80-84 75-79 MALE FEMALE 70-74 65-69 60-64 Age 55-59 YEMEN, 1975 Census 50-54 85+ 45-49 80 40-44 MALE FEMALE 35-39 75 30-34 25-29 70 20-24 65 15-19 10-14 60 5-9 55 0-4 50 1,500,000 750,000Population 0 750,000 1,500,000 45 40 35 ° Age misreporting errors (heaping) among adults 30 25 ° Under enumeration of young children (< age 2) 20 15 ° High fertility level 10 5 ° Smaller population in 20-24 age group 0 >> extraordinary events in 1950-55? 320,000 220,000 120,000 20,000 80,000 180,000 280,000 Population ° 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 90 MALE FEMALE 85 Age TUNISIA, 1994 Census 80 100+ 75 95 70 90 MALE FEMALE 65 Age heaping 85 60 80 55 75 50 70 45 65 40 60 35 55 30 50 25 45 20 40 15 35 10 30 5 25 0 20 100,00075,000 50,000 25,000 0 25,000 50,000 75,000100,000 15 Population 10 5 Declining fertility 0 120,00090,000 60,000 30,000 0 30,000 60,000 90,000120,000 Population
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 Bahrain, 2010 Census Age U.A.E., 2005 Census 85+ 80 MALE FEMALE 80-84 75 MALE FEMALE 70 70-74 65 60 60-64 55 50 50-54 45 40 40-44 35 30 30-34 25 20 20-24 15 10 10-14 5 0 0-4 30,000 20,000 10,000 0 10,000 20,000 30,000 500,000 300,000 100,000 100,000 300,000 500,000 Population 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 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 3,000,000 Age Bangladesh, 2001 Census 85+ Male 80 FEMALE 2,500,000 75 MALE Female 70 65 2,000,000 60 55 50 45 1,500,000 40 35 Population 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 3,000,000 9,000,000 Male 8,000,000 Male 2,500,000 Female 7,000,000 Female
6,000,000 2,000,000 5,000,000
1,500,000 4,000,000 Population
Population 3,000,000 1,000,000 2,000,000
500,000 1,000,000 0 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 7580+ 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 1997 Census 2007 Census Birth Cohort Male Female Male Female 0-4 1,353,206 1,388,350 2002-2007 5-9 1,112,321 1,113,675 1997-2001 ° Data is organized by birth 10-14 947,236 878,429 1,222,668 1,183,939 1992-1997 cohort 15-19 774,327 854,078 925,729 991,323 1987-1992 ° Exclude open-ended age 20-24 637,113 827,614 774,413 986,526 1982-1997 25-29 509,109 654,465 707,603 841,416 1977-1982 category 30-34 410,148 477,562 583,689 667,865 1972-1977 ° People who were born in 35-39 373,813 428,395 481,396 556,191 1967-1972 40-44 270,046 303,147 366,518 389,087 1962-1967 the same years are 45-49 257,070 282,098 321,236 328,660 1957-1962 compared in the analysis 50-54 178,902 212,060 231,232 283,288 1952-1957 55-59 162,122 174,234 194,011 208,657 1947-1952 60-64 114,335 125,096 140,146 159,557 1942-1947 65-69 100,425 109,288 113,840 127,794 1937-1942 70-74 47,407 50,607 72,288 81,329 1932-1937 75-79 41,529 42,858 55,448 61,012 1927-1932 Source : United Nations Statistics Division, 80-84 15,305 17,326 22,417 28,278 1922-1927 Demographic Yearbook Statistical 85-89 16,576 19,448 1917-1922 Database 90-94 4,803 5,883 1912-1917
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 1,400,000 FEMALE Male - 1997 Census Female - 1997 Census 1,200,000 1,200,000 Male - 2007 Census Female - 2007 Census 1,000,000 1,000,000
800,000 800,000 Population Population 600,000 600,000
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 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 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 2,000,000 Male - 2010 Census
1,500,000
1,000,000 Population
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 2,000,000 Female - 2010 Census
1,500,000
1,000,000 Population
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 ∗
= The age ratio for the age group to 4 5 = 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 Mozambique – 2007 Census 1.4 1.4
1.2 1.2
1 1
0.8 0.8
0.6 0.6 Age ratio Age ratio
0.4 0.4 Male Male 0.2 0.2 Female Female 0 0 5-9 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 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 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 Sex Ratio = or 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
100
90
80
70
60
50
40 1950 30 1975 20
Sex ratio (Number of men(Number 100of Sex women) perratio 2000 10 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 140 1997 Census 120 2007 Census
100
80
Rather sex ratio: 60 No decline at adult and older ages: > Under-enumeration > Higher female mortality? of boys? 40 > Higher female out-migration? > Higher male child > Under-enumeration of adult and older women? mortality? 20 > … Sex ratio (number of men per 100 women) per 100 men of (number ratio Sex 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
Republic of Korea, 2000 and 2010 Censuses 120
100 > Excess of men in 1975-1980 birth 80 cohort in 2000 census only 60
40 > Other age groups: 2000 Census as expected 20 2010 Census Sex ratio (number of men per 100 women) per 100 men of (number ratio Sex 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 Mozambique, 1997 and 2007 Censuses 120
100 > Very different patterns found in 80 each census
60 > Some consistencies 40 for birth cohorts 1947-1952 to 1927- 20 1997 Census 1932 2007 Census Sex ratio (Number of men per 100 women) 100 men per of (Number ratio Sex 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