IDEAS home Printed from
MyIDEAS: Log in (now much improved!) to save this paper

The Sensitivity of Estimates of Post-Apartheid Changes in South African Poverty and Inequality to key Data Imputations

Listed author(s):
  • Cally Ardington


    (SALDRU, School of Economics, University of Cape Town)

  • David Lam


    (Economics Department, University of Michigan)

  • Murray Leibbrandt


    (SALDRU, School of Economics, University of Cape Town)

  • Matthew Welch


    (DataFirst, University of Cape Town)

We begin by summarising the literature that has assessed medium-run changes in poverty and inequality in South Africa using census data. According to this literature, over the 1996 to 2001 period both poverty and inequality increased. In this paper we assesses the robustness of these results to the large percentage of individuals and households in both censuses for whom personal income data is missing and to the fact that personal income is collected in income bands rather than as point estimates. First, we use a sequential regression multiple imputation approach to impute missing values for the 2001 census data. Relative to the existing literature, the imputation results lead to estimates of mean income and inequality (as measured by the Gini coefficient) that are higher and estimates of poverty that are lower. This is true even accounting for the wider confidence intervals that arise from the uncertainty that the imputations bring into the estimation process. Next we go on to assess the influence of dubious zero values by setting them to missing and re-doing the multiple imputation process. This increases the uncertainty associated with the imputation process as reflected in wider confidence intervals on all estimates and only the Gini coefficient is significantly different from the first set of estimated parameters. The final imputation exercise assesses the sensitivity of results to the practice of taking personal incomes recorded in bands and attributing band midpoints to them. We impute an alternative set of intra-band point incomes by replicating the intra-band empirical distribution of personal incomes from a national income and expenditure survey undertaken in the year before each census. Using the empirical distributions increases estimated inequality although the differences are relatively small. We finish our empirical work with a discussion of provincial poverty shares as a policy relevant illustration of the importance of dealing with missing values. Overall our results for 1996 and 2001 confirm the major findings from the existing literature while generating more reliable confidence intervals for the key parameter of interest than are available elsewhere.

If you experience problems downloading a file, check if you have the proper application to view it first. In case of further problems read the IDEAS help page. Note that these files are not on the IDEAS site. Please be patient as the files may be large.

File URL:,com_docman/Itemid,33/gid,218/task,doc_download/
Download Restriction: no

Paper provided by Southern Africa Labour and Development Research Unit, University of Cape Town in its series SALDRU/CSSR Working Papers with number 106.

in new window

Date of creation: 2005
Handle: RePEc:ldr:cssrwp:106
Contact details of provider: Postal:
Private BagX3, Rondebosch, 7701, Cape Town

Phone: +27 21 650 5696
Fax: +27 21 650 5697
Web page:

More information through EDIRC

References listed on IDEAS
Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.:

in new window

  1. Murray Leibbrandt & Laura Poswell & Pranushka & Matthew Welch & Ingrid Woolard, 2004. "Measuring recent changes in South African inequality and poverty using 1996 and 2001 census data," SALDRU/CSSR Working Papers 084, Southern Africa Labour and Development Research Unit, University of Cape Town.
Full references (including those not matched with items on IDEAS)

This item is not listed on Wikipedia, on a reading list or among the top items on IDEAS.

When requesting a correction, please mention this item's handle: RePEc:ldr:cssrwp:106. See general information about how to correct material in RePEc.

For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: (Alison Siljeur)

If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

If references are entirely missing, you can add them using this form.

If the full references list an item that is present in RePEc, but the system did not link to it, you can help with this form.

If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your profile, as there may be some citations waiting for confirmation.

Please note that corrections may take a couple of weeks to filter through the various RePEc services.

This information is provided to you by IDEAS at the Research Division of the Federal Reserve Bank of St. Louis using RePEc data.