OpenUCT :: Browsing by Author "Dorrington, Rob"

Browsing by Author "Dorrington, Rob"

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Open Access
An assessment of the feasibility of using administrative data in producing mid-year population estimates for South Africa
(2015) Hlabano, Mbongeni Charles; Dorrington, Rob
The production of mid-year population estimates is an important undertaking which informs various stakeholders in policy formation and decision making. For instance, national governments use mid-year estimates to allocate seats in parliament to various constituents and public health sectors use them to monitor and improve service delivery. Mid-year population estimates undoubtedly serve very important purposes that affect lives of many people. As such, national statistical offices in various countries are given the mandate to produce annual mid-year population estimates. Statistics South Africa (Stats SA) assumes the function of producing and publishing official mid-year estimates of the population in South Africa. Stats SA produces its mid-year estimates using DemProj, population projection software which is part of the SPECTRUM suite of policy models developed by the Futures Institute. However, Stats SA does not publish full details of its adaptation of DemProj when producing its mid-year estimates as it regards this as proprietary. Concerns have been raised about the accuracy of the official mid-year estimates in terms of age distribution, particularly for ages below 40 last birthday in 2011 (e.g. Dorrington 2013). As such, this research critically analyses the method used by Stats SA to produce mid-year estimates and assesses the feasibility of using administrative data to produce mid-year estimates for South Africa. The base population is adapted from the 2001 census population. Birth and death registration data are used in a cohort component approach to produce alternative mid-year estimates for South Africa for the years 2002-2011. Prior to using these data, they are adjusted for incompleteness of registration. Levels of completeness of birth and death registration are estimated by extrapolating earlier estimates of completeness from various researchers. The mid-year estimates obtained are compared with those published by Stats SA in order to assess the relative quality of the two series of mid-year estimates. The mid-year estimates for 2011 are also compared with the mid-year population estimated from the 2011 census. These comparisons help identify the mismatches to the census and their possible causes and as such, these may lead to improved population estimates in the future, and a viable alternative method to that currently being used by Stats SA.
Open Access
Assessment of the IGME methods of estimating infant mortality rate and neonatal mortality rate from under-five mortality rate in countries affected by HIV
(2012) Ayalew, Kassahun Abere; Dorrington, Rob
This study assesses the UN Inter-agency Group for Child Mortality Estimation (IGME) methods of estimating the infant and neonatal mortality rates from the under-five mortality rates in countries affected by HIV/AIDS. It uses Botswana, Malawi and South Africa as case studies. The assessment is made by comparing the IGME results with estimates from projection models and empirical results computed from survey data and vital statistics data corrected for the level of incompleteness for the countries included in the study. In addition, relevant literature is reviewed in order to determine the reasonableness and impact (on the results produced) of the assumptions made by the method.
Open Access
Assessment of the robustness of recent births in estimating infant mortality using multi-country Demographic Health Survey data
(2014) Munjoma, Malvern; Moultrie, Tom; Dorrington, Rob
This dissertation investigates the robustness of recent births in estimating infant mortality rates from the proportion of deaths observed among births reported in a 24month period. The Blacker Brass technique is applied to all births reported in the 24month period and to most recent births in the 24 month period. The study uses birth history data from 76 Demographic and Health Surveys conducted in 16 countries across the developing world between 1986 and 2011. All births (and the deaths of those births) occurring in five 2-year periods before each survey were extracted to obtain five estimates of infant mortality using the Blacker-Brass and direct estimation methods from each dataset. This allows trends in infant mortality for the 10-year period before the survey to be compared and relative errors to be calculated. The results showed a decline in infant mortality in most datasets and are consistent with the United Nations and the World Health Organisation 2013 estimates. The relative errors did not indicate any systematic bias of the Blacker-Brass method applied to all births; however, further investigations showed that the method underestimated infant mortality in the period closest to the survey date in most datasets. Furthermore, the relative errors were positively correlated with the directly estimated level of infant mortality. There were, however, no significant differences in the relative errors across countries.
Open Access
Child and adult mortality in Zimbabwe, 1980-2005
(2011) Marera, Double-Hugh; Dorrington, Rob
This research applies direct and indirect methods to data from censuses and Demographic and Health Surveys to derive empirical estimates of the level and trends of child and adult mortality in Zimbabwe from 1980 to 2005.
Open Access
Child mortality in South Africa - we have lost touch
(2007) Bradshaw, Debbie; Dorrington, Rob
Reducing child mortality is, appropriately, one of the eight Millennium Development Goals (MDGs) for reducing poverty and inequality in the world. The target for this goal is to reduce child mortality by 2015 by two-thirds of the rate in 1990. Monitoring child mortality rates, however, is posing a challenge for low- and middle-income countries. Estimates that many countries, particularly in Africa, use to track progress in meeting this goal have to be extrapolated from earlier empirical data, since there are no up-to-date data. Despite great strides that have been made in improving population health statistics, South Africa is unfortunately no exception. The most recent reasonably reliable estimates of child mortality for South Africa are for the mid-1990s, in other words 10 years out of date.
Open Access
Completeness of death registration in Cape Town and its health districts, 1996-2004
(2007) Zinyakatira, Nesbert; Dorrington, Rob
It is important for health planners to have timeous and accurate data on deaths. The Department of Home Affairs is responsible for the registration of deaths and the City of Cape Town has a well-established system of collating the death statistics based on vital registration, but the completeness of the death registration has not been assessed previously. The completeness was assessed for the City of Cape Town by comparing their statistics with an estimate based on data obtained from adult deaths reported in the 2001 census. A second approach assessed the trend in completeness between 1996 and 2004 by identifying three rates of mortality considered to be stable over time (non-lung and non-oesophageal cancers, the 10-14 age group and the 60+ age group) and inspecting to observe whether there was any trend apparent over time. Since deaths in most cases are under reported, and the under reporting usually differs in completeness between children and adults, child deaths from the ASSA model projection assuming that they are more complete were compared with the child deaths from the vital registration between 1996 and 2004 to check for completeness of the child vital registration data in Cape Town and its eight health districts The results show high levels of completeness in the adult deaths for Cape Town as a whole in 2001, around 95 per cent, but varying levels in the health districts. The completeness of reporting of male deaths in Cape Town declines with age, whilst completeness for females is fairly level with respect to age, with similar trends being observed in the health districts. Completeness of child (0 -4) death registration averaged around 60 per cent, about 35 per cent lower than the completeness of adult deaths in Cape Town. Cape Town as a whole and most of its health districts revealed two levels of completeness in the registration of deaths, 1996-1999 and 2001-2004 with 2000 sometimes consistent with the first and sometimes with the second period or different from either period in some of the health districts. In conclusion, the completeness estimates obtained are more rigorous from 2001 onwards suggesting that they can be reliably used to monitor trends in the levels of mortality in the city of Cape Town.
Open Access
The construction of a price index for the South African Medical Scheme Industry
(2010) Ramjee, Shivani; Dorrington, Rob
A methodology is proposed for constructing a price index that reflects the change in the prices of the goods and services purchased by medical schemes in South Africa. The methodological choices were made taking cognisance of the unique characteristics of the South African medical scheme environment, both in terms of the factors influencing the mix of goods and services purchased by medical schemes, as well as the factors affecting price determination. An example of a pharmaceutical price index was constructed to illustrate the proposed methodology, the results of which are presented. Whilst the proposed methodology provides a base for creating a meaningful and useful medical scheme price index there is considerable further work that needs to be done to refine the methodology.
Open Access
Does the 2008 HSRC survey indicate a turning tide of HIV prevalence in children, teenagers and the youth?
(2009) Dorrington, Rob
Recently the HSRC released its report on the results of its third and most recent household prevalence survey. The main conclusion of their analysis is that “some solid progress has been made in the fight against the disease in the past few years, especially among teenagers and children”. In particular the authors conclude: • that HIV prevalence at national level has decreased amongst children aged 2-14, from 5.6% in 2002 to 2.5% in 2008, • that there was a substantial decrease in incidence in 2008 in comparison to 2002 and 2005, especially for the single age groups 15, 16, 17, 18, and 19, • that HIV prevalence has decreased amongst youth aged 15-24 from 10.3% in 2005 to 8.6% in 2008, and • that HIV prevalence among adults aged 15-49 has declined between 2002 and 2008 in the Western Cape, Gauteng, Northern Cape and the Free State, “with the largest decline of 7.9 (sic) percentage points in the Western Cape”. How reliable are the results from the survey and how reasonable are these conclusions?
Open Access
The effect of HIV on the orphanhood method of estimating adult female mortality
(2009) Kramer, Stephen; Dorrington, Rob
The orphanhood method of estimating adult mortality is widely used in developing countries. The method is subject to a number of assumptions, some of which are violated when a generalized high-prevalence HIV epidemic is present. Non-independence of the mortality of children and mothers, relationships between HIV infection and fertility, and changes in age-specific mortality result in biases that affect the accuracy of the method. An earlier study has examined some of these sources of error, and proposed adjustments to enable continued use of the method. This earlier research, however, uses data from populations with lower HIV prevalence rates than are currently being experienced in much of southern Africa, and is based on specific assumptions about HIV and its effects on mortality and fertility. The effects of HIV on the method are investigated in this research using mathematical modelling of the effects on Black South African females - a population with high HIV prevalence. More is now known about HIV and its effects on mortality and fertility, and these effects are explicitly reflected in the ASSA2002 model which provides much of the data for this research. The research compares the simulated survival of various cohorts of women: those aged 25 in a certain year, women (with an age profile identical to that of mothers), mothers, and mothers as reported by their children. In this way the various sources of error are explicitly identified and the errors quantified. The timing, magnitude, and combined effects of the errors are studied in relation to the emergence and spread of HIV, indicating when the errors might be expected to be large enough to invalidate the method. Errors that bias the outcomes of the orphanhood method take a number of years to develop after HIV starts spreading. Substantial biases in reported survival emerge between 20 and 35 years after the start of an HIV epidemic, in a high prevalence setting. These errors are reduced by the use of antiretroviral and prevention of mother-to-child transmission, but biases remain large enough to invalidate outcomes when the unadjusted method is applied in most southern African countries. An adjusted method has been proposed which substantially reduces error, except when adjusting survival reported by the two youngest age groups. This adjusted method can be applied, but further research to identify revised adjustments would further improve the accuracy of the method.
Open Access
The effect of HIV/AIDS on the own child-method of estimating child mortality : Lesotho and Zimbabwe
(2011) Musariri, Herbert; Dorrington, Rob
This study evaluates the overall impact of the bias due to HIV/AIDS on the own-child method of estimating child mortality, and the contribution of the various components to the overall bias. Indirect estimates of child mortality are calculated by applying the own-child method to the 2009 Lesotho Demographic and Health Survey (LDHS) and the 2005-6 Zimbabwe DHS. In the process, the potential of the software, MATCHTAB, to link successfully surviving children to their biological mothers is demonstrated using the 2006 Lesotho census data. To evaluate the impact of HIV/AIDS on the own-child method, the target estimates of child mortality for Lesotho and Zimbabwe are also developed by adjusting the direct estimates from the full history data for the selection has introduced by HIV/AIDS.
Open Access
Estimates of the level and shape of mortality rates in South Africa around 1985 and 1990 derived by applying indirect demographic techniques to reported deaths
(1998) Dorrington, Rob; Bradshaw, Debbie; Wegner, Trevor
This research attempts firstly to estimate both the level and shape of the mortality curve of the Black South African population group circa 1985 by the application of indirect demographic techniques to the reported deaths for Blacks for the period 1984- 86 and an estimate of the Black population in mid-1985. The life tables thus produced are then combined with the official South African Life Tables for Whites, Coloureds and Asians to produce a weighted average national life tables circa 1985. These national life tables are then compared with those produced by applying the Bennett and Horiuchi method to national data for the 1984-86 period in order to decide on suitable adjustments to make when applying the Bennett and Horiuchi method to national data for the period 1989-91 and beyond.
Open Access
Estimating adult mortality in South Africa using information on the year-of-death of parents from the 2016 Community Survey
Mambwe, Chibwe; Dorrington, Rob
In developing countries, systems that collect vital statistics are usually inadequate to facilitate the direct estimation of adult mortality. This has necessitated the development of indirect methods such as the orphanhood method. These methods are however limited, i.e., the single-survey approach produces out of date estimates of mortality and the two-survey approach is affected by the differential reporting of orphanhood between two surveys. To avoid these limitations, this research considers an extension of the orphanhood approach pioneered by Chackiel and Orellana (1985) to estimate adult mortality using year-of-death data rather than the conventional form of the orphanhood data. This is because the year-of- death data can be used to produce accurate time locations to which estimates of mortality apply but more important, one can create a synthetic survey from a single survey and hence obtain more recent and accurate estimates of mortality. The single-survey orphanhood method is applied to survey data to obtain estimates of adult mortality and time location. A variation of the two-survey orphanhood method (Timæus 1991b) is also applied to survey data and the synthetic survey that is created from year-of-death data in order to derive estimates of adult mortality. In addition, the age range of respondents is extended down to age O to include year-of-death data from younger respondents on the assumption that underestimating orphanhood due to the adoption effect is minimal. This is done to investigate if the estimates derived from the two-survey method can be improved. Further, a cohort survival method that involves the calculation of a survival ratio for each age group at the first survey and the equivalent older ages groups at the second survey is applied to investigate the possibility of producing useful estimates of adult mortality based on cohort survival. The level and trend in mortality estimates calculated from the single-survey, two - survey and the cohort survival approaches are discussed and compared to the estimates from the Rapid Mortality Surveillance (RMS) which are used as a benchmark for the trend and level of adult mortality in South Africa. The estimates produced using the single-survey method appear too low, while those from the two-survey method appear to be reasonable for the conventional from of the orphanhood data. Extending the two-survey method to include younger respondents produces estimates that are too low indicating that both the conventional form of the orphanhood data and the year-of-death data suffer from the adoption effect. The cohort survival approach produces reasonable estimates that are consistent with the RMS benchmark for both the conventional form of the orphanhood data and year-of-death data.
Open Access
Estimating adult mortality in South Africa using orphanhood and year of death data from the 2008 National Income Dynamics Study
(2010) Kupamupindi, Takura; Dorrington, Rob
The overall objective of this research is to investigate whether using year of death data to produce estimates of time location is a better approach than the method developed by Brass and Bamgboye (1981) and whether estimates of mortality produced using year of death data are any better than those derived using the conventional orphanhood method.
Open Access
Estimating the level and trends of child mortality in South Africa, 1996-2006
(2009) Darikwa, Timotheus Brian; Dorrington, Rob
The lack of reliable data for child mortality estimation since 1998 has meant that child mortality rates for South Africa have not been updated for almost ten years now. It is the overall aim of this research to explore the possibility of determining up-to-date estimates of South Africa's infant mortality and under-five mortality rates from the 2007 Community Survey data and to use these results to describe the trend in child mortality rates since 1996.
Open Access
Estimating the risks in defined benefit pension funds under the constraints of PF117
(2017) Mahmood, Ra'ees; Kendal, Shannon; Dorrington, Rob
With the issuing of Pension Funds circular PF117 in 2004 in South Africa, regulation required valuation assumptions for defined benefit pension funds to be on a best-estimate basis. Allowance for prudence was to be made through explicit contingency reserves, in order to increase reporting transparency. These reserves for prudence, however, were not permitted to put the fund into deficit (the no-deficit clause). Analysis is conducted to understand the risk that PF117 poses to pension fund sponsors and members under two key measures: contribution rate risk and solvency risk. A stochastic model of a typical South African defined benefit fund is constructed with simulations run to determine the impact of the PF117 requirements. Findings show that a best-estimate funding basis, coupled with the no-deficit clause, results in significant risk under both contribution rate and solvency risk measures, particularly in the short-term. To mitigate these risks, alternative ways of introducing conservatism into the funding basis are required, with possible options including incorporating margins into investment return assumptions or the removal of the no-deficit clause.
Open Access
The estimation and interpretation of adult mortality rates of African South Africans using Census 2001 data
(2009) Dobbie, Mark-Ross B; Dorrington, Rob
This research develops estimates of mortality rates for adult Africans in South Africa for the twelve months preceding the census night, 9/10 October 2Q(B, using Census 2001 10% sample data. The approach used to estimate these rates follow the work done by Dorrington, Moultrie and Timaeus (2004) working with the full dataset, which is not publicly anilable, and demonstrate that the 10% sample can be used to produce similar results to the full database. The approach makes use of indirect estimation techniques for estimating the completeness of reporting of deaths in the vital registration system at a national level, namely the combination of Generalized Growth Balance method (GGB) and the Synthetic Extinct Generations (SEG) method adapted to allow for net immigration over the inter-censal period.
Open Access
Estimation of the level and trend of adult motrality in Zambia
(2010) Chisumpa, Vesper Hichilombwe; Dorrington, Rob
The aim of this study is derive robust and reliable estimates of level and trend in adult mortality in Zambia. To derive the estimates of the level and trend in adult mortality, the study applies the following techniques: the Census Survival method and Preston-Bennett method to Zambian census data for 1980, 1990 and 2000 to estimate life expectancies at age 5 and above as well as probabilities of dying between ages 15 and 60 years; the orphanhood method to 1992, 1996, 2001/2 and 2007 Zambia Demographic and Health Surveys (ZDHS) and 1996, 1998, 2002/3, 2004 and 2006 Living Conditions Monitoring Survey (LCMS) information on survivorship of parents to estimate probabilities of dying between ages 25 and 35 ( 10 25 q ); and 25 and 40 ( 15 25 q ) for females; and 35 and 45 ( 10 35 q ) for males; the siblinghood method using the 1996, 2001/2 and 2007 ZDHS sibling histories data to estimate the probabilities of dying between ages 15 and 50 years ( 35 15 q ) for both males and females; the Generalised Growth Balance and Bennett-Horiuchi 'Extended SEG' methods using the 1996, 2004 and 2006 LCMS household deaths in the last 12 months to estimate completeness of reporting of deaths relative to the coverage of surveys and hence the probability of dying between ages 15 and 60. The Census Survival and Preston-Bennett method do not produce accurate measures of mortality, or trend for females but does for males. The orphanhood method does capture some of the trend but fails to provide definitive estimates of mortality. The siblinghood method produces an inconclusive pattern of adult mortality. The GGB and 'Extended SEG' methods perform well with the 1996- 2004, 1996-2006 inter-survey periods. The methods also perform well with male LCMS data for 2004-2006 inter-survey periods. The GGB and 'Extended SEG' methods produced a good fit to age ranges 5+ to 60+. The study finds that adult female mortality is higher than male adult mortality, 69 per cent and 64 per cent, respectively. These adult mortality rates are comparable to estimates from other sources. Further research is needed on how to refine the GGB and SEG method to perform better with survey data. Research is needed to understand why the siblinghood method produced inconclusive estimates of the level and trend of adult mortality. The study recommends that the LCMS survey should add month and year at death to questions on household deaths to deal with the problem of time reference. The 2010 Zambian census should add questions on orphanhood and household deaths.
Open Access
Evaluating the adequacy of the method of using vital registration and census data in estimating adult mortality when applied sub-provincially
(2017) Chinogurei, Chido; Dorrington, Rob
In developing countries, vital registration is the best source of death data that can be used to estimate adult mortality provided they are sufficiently complete. However, they are usually insufficient for estimating mortality sub-nationally due to incomplete registration. This research adapts a method used by Dorrington, Moultrie and Timæus at the provincial level to determine whether it is adequate for estimating adult mortality at the district municipality level in the year prior to the 2001 census. The method uses registration data adjusted for completeness of registration to scale (up or down) the deaths reported by households in the census by age group for each sex. The process of correcting the registered deaths in the year prior to the 2001 census involves estimating intercensal completeness for each population group and each sex between 1996 and 2001 using the average of results from the GGB and the SEG+δ methods. Thereafter, the results are used to estimate the completeness in each of the years within the intercensal period. Thus, an estimate of completeness is obtained in the year prior to the 2001 census for correcting the registered deaths at the population group level. These registered deaths are then used to obtain population group specific adjustment factors to correct the deaths reported by households at the district level, and thereafter to estimate adult mortality rates. Most districts in Kwa-Zulu-Natal have amongst the highest rates of adult mortality, while most districts in the Western Cape have amongst the lowest rates. Results show the Buffalo metropolitan municipality to have higher mortality than that expected for most of the district metropolitan municipalities for both sexes. The same is true for women in Mangaung metropolitan district. It is suspected that HIV prevalence had a significant impact on different levels of adult mortality in the districts, although some adults in the more urban provinces may have died in other provinces. At the provincial level, the method produces marginally higher estimates of adult mortality than the other sources. Provinces that reflect a higher level of mortality appear to deviate more from other research findings than those reflecting lower mortality. In conclusion, the method produces district estimates of ₄₅q₁₅ that are consistent with provincial estimates from other sources and with estimates of HIV prevalence at the district level.
Open Access
Flaws, approximations and uncertainties in the estimation of the exposed-to-risk
(1991) Slawski, J K; Dorrington, Rob
This research analyses the theoretical basis of exposed-to-risk estimation. It defends the conventional actuarial approach against criticisms raised by Hoem (1984), and, in so doing, examines in detail the development of the actuarial profession's estimation techniques. Maximum likelihood estimates are shown to be closely related to the estimates of decremental probabilities derived using the conventional actuarial approach. The correct treatment of deaths when estimating the initial exposed-to-risk is considered and contrasted with what is often used in practice. The relationship between the initial and central exposed-to-risk is considered for a single decrement, two decrements and for select rates. The implications of alternative assumptions and approximations are considered. Some inaccuracies in tuition material of the Faculty and Institute of Actuaries and articles written about exposed-to-risk are highlighted. Other problem areas, such as the bias of calculated rates and estimation under policy and calendar year rate intervals, are also considered.
Open Access
Full life tables for South Africa from vital registration data, 2006-2008
(2011) Marandu, Simon Hlomayi; Dorrington, Rob
This research derives a set of full life tables for South Africa as a whole and by population group using vital registration data for the period 2006-2008. Given that not all deaths are registered, the research assesses the level of completeness of death registration for the national population and for all the population groups separately by using the deaths distribution methods.