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EquityTool: Released 15 October 2020
Source data: Burkina Faso MIS 2017
# of survey questions in original wealth index: 36
# of variables in original index: 105
# of survey questions in EquityTool: 15
# of variables in EquityTool: 17
|Question||Option 1||Option 2||Option 3||Option 4|
|Determine if respondent lives in an urban or rural area:||Urban||Rural|
|Q1||In your household, do you have : …electricity?||Yes||No|
|Q6||Does any member of your household own : …a motorcycle/scooter?||Yes||No|
|Q7||…an animal-drawn cart?||Yes||No|
|Q8||Does any member of your household have a bank account?||Yes||No|
|Q9||What kind of toilet facility do members of your household usually use?||No facility/bush/field||Other|
|Q10||What type of fuel does your household mainly use for cooking?||Wood||Other|
|Q11||What is the main material of the floor of your house?||Cement||Earth/sand||Other|
|Q12||What is the main material of the roof of your house?||Sheet metal||Other|
|Q13||What is the main material of the walls of your house?||Earth||Other|
|Q14||Among the following animals, how many does your household own: …Goats?||None||1 to 4||5 to 9||10 or more
|Q15||…Sheep?||None||1 to 9||10 or more|
The EquityTool creation process relies upon the scores published by the DHS Program. The scores are available as an excel file, and the original SPSS syntax used to create the wealth index is also published. In the case of Burkina Faso, we noticed a discrepancy between the list of variables and factor weights provided in the excel file, and the original syntax. A query to the DHS team is unresolved. Therefore, we recreated the wealth index using the same variables and process indicated in the published syntax, and used the resulting factor weights to create the EquityTool. Of note, the Burkina Faso index differs from most other indices in one notable area which affected our final tool – when asking about the presence of animals, the index does not explicitly include a variable for no ownership of a particular animal. Additionally, in the original syntax, and our simplification, the urban index had to be reversed.
Separate urban and rural indices to create a national EquityTool
We were unable to achieve a reduced set of questions at a high level of agreement using our standard approach for the Burkina Faso MIS 2017. Using a revised approached, detailed below, high agreement (kappa >= 0.75 for both urban and national indices) was achieved. Our standard simplification process is detailed in this article. The national factor weights used in that approach come from an analysis of the national population and contain only those variables which are related to the construct of wealth in the same way in both rural and urban areas. The national factor weights are usually used in EquityTools to calculate national quintiles, as they reduce some known areas of respondent error in the survey.
However, to overcome the problem of low agreement using the standard simplification approach, we instead used factor weights from the rural and urban analyses, which select variables that related to wealth differently in urban and rural areas. For example, in an urban area, ownership of goats may be more strongly associated with being relatively poor than in rural areas. This is the case in Burkina Faso. A short list of variables, common to both urban and rural areas, were iteratively selected to find those which result in high agreement (kappa>=0.75) against the original wealth index quintiles for national and urban populations. The data used to identify important variables comes from the recreated wealth index. For Burkina Faso, the scores for urban and rural residents were combined into a national score using linear regressions, in a process similar to that used by ICF. Specifically, a score from the simplified index for urban residents (Uscore) was regressed against the wealth index score variable created for the corrected full wealth index analysis (Nscore), the same was done for rural residents (Rscore), and the resulting coefficients are used to create a single national score (NatScore).
Nscore=b1Uscore + a1
Where Urban=1 if respondent lives in an urban area and 0 if otherwise, and Rural =1 if respondent lives in a rural area and 0 if otherwise.
Respondents quintile assignments resulting from NatScore, the national wealth index score created from a simplified list of questions, were compared to the quintile assignments resulting from the original wealth index with 105 variables using the kappa statistic.
The questions in the simplified index which resulted from this process differ from EquityTools that are created using our standard approach. Notably, we need to know whether the respondent lives in an urban or rural area, thus an additional question has been added to the EquityTool for Burkina Faso: 'Determine if the respondent lives in an urban or rural area'. In principle, the definition of 'urban' and 'rural' should match the definition used in the Burkina Faso MIS 2017. Typically, this definition is defined by the country, not the developers of the DHS. In practice, the user needs to decide how to determine if each respondent lives in an urban or rural area. Three approaches are presented below, with some notes on each. Whichever method is chosen, it should be uniformly applied across all surveys conducted.
- Ask the respondent directly – 'is your home in an urban or rural area?' This relies on the respondent's understanding of 'urban' and 'rural'.
- Allow the data collector to determine whether the respondent lives in an urban or rural area, based on available guidance. This will work best if the interviews take place in or very near to people's homes, and if the data collectors can be trained on the same rules to determine if an area is urban or rural. One example of a rule is to classify 'peri-urban' areas on the edges of a city or town as urban. Another rule might be to classify an area as urban if it has a market center which operates daily.
- If the interviews are taking place outside the home, then classify respondents based upon the location of the interview. For example, if interviews occur in health facilities, classify respondents as urban if the facilities are located in urban areas. Individuals may travel, so this method is also subject to error.
Level of agreement:
|Urban only population
Respondents in the original dataset were divided into three groups for analysis – those in the 1st and 2ndquintiles (poorest 40%), those in the 3rd quintile, and those in the 4th and 5th quintiles (richest 40%). After calculating their wealth using the simplified index, they were again divided into the same three groups for analysis against the original data in the full DHS. Agreement between the original data and our simplified index is presented above.
What does this mean?
When shortening and simplifying the index to make it easier for programs to use to assess equity, it no longer matches the original index with 100% accuracy. At an aggregate level, this error is minimal, and this methodology was deemed acceptable for programmatic use by an expert panel. However, for any given individual, especially those already at a boundary between two quintiles, the quintile the EquityTool assigns them to may differ to their quintile according to the original DHS wealth index.
The graph below illustrates the difference between the EquityTool generated index and the full DHS wealth index. Among all of those people (20% of the population) originally identified as being in the poorest quintile, approximately 82.0% are still identified as being in the poorest quintile when we use the simplified index. However, approximately 16.5% of people are now classified as being in Quintile 2. From a practical standpoint, all of these people are relatively poor. Yet, it is worthwhile to understand that the simplified index of 15 questions produces results that are not identical to using all 36 questions in the original survey.
The following table provides the same information on the movement between national quintiles when using the EquityTool versus the original DHS wealth index:
|EquityTool National Quintiles|
|Quintile 1||Quintile 2||Quintile 3||Quintile 4||Quintile 5||Total|
|Original DHS National Quintiles||Quintile 1||16.4%||3.3%||0.2%||0.1%||0.0%||20%|
The following graph provides information on the movement between urban quintiles when using the EquityTool versus the original DHS wealth index:
The following table provides the same information on the movement between urban quintiles when using the EquityTool versus the original DHS wealth index:
|EquityTool Urban Quintiles|
|Quintile 1||Quintile 2||Quintile 3||Quintile 4||Quintile 5||Total|
|Original DHS Urban Quintiles||Quintile 1||17.1%||2.9%||0.0%||0.0%||0.0%||20%|
Data interpretation considerations:
- This tool provides information on relative wealth – 'ranking' respondents within the national or urban population. The most recent available data from the WorldBank indicates that 43.8% of people in Burkina Faso live below $1.90/day. This information can be used to put relative wealth into context.
- People who live in urban areas are more likely to be wealthy. In Burkina Faso, 78.5% of people living in urban areas are in the richest national quintile, compared to only 6.3% of those living in rural areas.
- If your population of interest is predominantly urban, we recommend you look at the urban results to understand how relatively wealthy or poor they are, in comparison to other urban dwellers.
- If the people you interviewed using the EquityTool live in rural areas, or a mix of urban and rural areas, we recommend using the national results to understand how relatively wealthy or poor they are, in comparison to the whole country.
- Some regions in Burkina Faso are wealthier than others. It is important to understand the country context when interpreting your results.
- In most cases, your population of interest is not expected to be equally distributed across the five wealth quintiles. For example, if your survey interviewed people exiting a shopping mall, you would probably expect most of them to be relatively wealthy.
Metrics for Management provides technical assistance services to those using the EquityTool, or wanting to collect data on the wealth of their program beneficiaries. Please contact firstname.lastname@example.org and we will assist you.
 From povertydata.worldbank.org, reporting Poverty headcount ratio at $1.90/day at 2011 international prices.
The Burkina Faso EquityTool was produced as a product supported by the 'Scale Up Cervical Cancer Elimination with Secondary prevention Strategy' project, funded by Unitaid, and led by Expertise France.