Factors influencing the comparability of poverty estimates across household surveys

ABSTRACT

The South African existing literature on poverty mainly adopted the money-metric approach to examine poverty levels and trends since the advent of democracy. In general, poverty increased until the end of the 1990s, before a downward trend took place. Despite the robust findings on the trends, poverty levels differed because of various reasons, ranging from the use of different poverty lines across the studies, to the adoption of different approaches to collect the income and expenditure information, and the presence of a high proportion of households reporting zero or unspecified income. This article aims to fill the existing research gap by explaining the possible factors accounting for the contrasting poverty levels across the eight commonly used South African censuses and household surveys between 1993 and 2012.

KEYWORDS:

• poverty
• income
• expenditure
• recall method
• diary method
• sequential regression multiple imputation

JEL CLASSIFICATION:

• I32

Acknowledgement

The author gratefully acknowledges the valuable comments by Servaas van der Berg.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes

¹This is the case in IES 2005/06 and 2010/11, as the participants were given a diary with blank pages to fill in the consumption activities.

²For more detailed explanation of the SRMI methodology, refer to Raghunathan et al. (2001), Ardington et al. (2006), Lacerda et al. (2008) and Vermaak (2008).

³Detailed explanation of the methodology of this approach falls beyond the scope of this study, but the reader can be referred to Wittenberg (2010:315–19) as well as Branson & Wittenberg (2014:26–8).

⁴At the time of writing, the author had requested the 2010–2012 AMPS data from the South African Advertising Research Foundation but did not receive a response.

⁵If a household had two (three) completed diaries, expenditure from the two (three) diaries was added together and the sum was divided by two (three). This average figure was then used to impute for the remaining two (one) non-completed/missing diaries (diary) (Stats SA, 2006).

⁶For a detailed discussion on the difference between the STC and COICOP approaches, refer to Yu (2008).

⁷Refer to Yu (2009) for detailed explanation on how SRMI was conducted.

⁸The proportion of households never experiencing adult hunger increased from 69% in GHS 2002 to above 80% in GHS 2006–12, while the proportion of households never experiencing child hunger increased from 69% to the 80 to 85% range in GHS 2006–12.

⁹For example, if the total monthly household income of a household was derived as R5500 in IES 1995, it is assumed that the household head would report that his/her household falls in the OHS 1996 ‘R5000–R9999’ category, the Census 1996 ‘R3201–R6400’ category and the AMPS 1995 ‘R5000–R5999’ category.