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EquityTool: Released July 28, 2020
Source data: Tunisia MICS 2018
# of survey questions in original wealth index: 42
# of variables in original index: 137
# of survey questions in EquityTool: 12
# of variables in EquityTool: 13
|Question||Option 1||Option 2||Option 3|
|DETERMINE IF THE RESPONDENT LIVES IN AN URBAN OR RURAL AREA
|Q1||Does your household have an electric oven?||Yes||No|
|Q2||Does any member of your household have a: computer or tablet?||Yes||No|
|Q3||… bank account or postal account?||Yes||No|
|Q4||What is the main material of the floor of your house?||Ceramic Tile||Other|
|Q5||In your household, what type of cook stove is mainly used for cooking?||Liquefied Petroleum Gas||Piped natural gas stove||Other|
|Q6||What does your household mainly use for space heating when needed?||Manufactured space heater||Other|
|Q7||What type of fuel and energy source is used for this heater?||Charcoal||Other|
|Q8||What is the main source of drinking water used by members of your household?||Bottled water||Other|
|Q9||What kind of toilet facility do members of your household usually use?||Flush to piped sewer system||Other|
|Q10||Does this household own any:… Milk cows or bulls?||No||Yes|
|Q12||… Horses, donkeys or mules?||No||Yes|
Recreating the full index
To create the EquityTool, we simplify the original full wealth index that is found in the relevant benchmark dataset, usually using published factor weights. In the case of MICS data, the factor weights are not publicly available, however UNICEF has shared the original syntax files used to create wealth indices with us. We attempted to recreate the original wealth index, following the original syntax files.
In the case of Tunisia MICS 2018, we were unable to replicate the analyses and results did not have access to the factor weights from the full wealth index. This led us to recreate the full wealth index, using a process in line with guidance from ICF. We used this recreated wealth index as the basis for the scoring we used in our EquityTool analysis.
Separate urban and rural indices to create a national EquityTool
We were unable to achieve agreement of kappa>=0.75 between the full wealth index and a simplified index using our standard simplification process (detailed in this article). Using a revised approach, detailed below, high agreement (kappa>=0.75 for both urban and national indices) was achieved. The data used to identify important variables came from our recreated full wealth index described above.
We were unable to achieve a reduction in questions or an agreement of kappa>=0.75 between the original wealth index quintiles and quintiles created using factor weights from the national factor weights for Tunisia MICS 2018. These national factor weights 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. These national factor weights are usually used in EquityTools to calculate national quintiles, as they reduce some known areas of respondent error in the survey.
To overcome this problem of low agreement, we instead used the factor weights from the rural and urban analyses, which select variables that relate to wealth differently in urban and rural areas. For example, in an urban area, ownership of chickens may be associated with being relatively poor, while in rural areas, it may be associated with being relatively wealthy. In Tunisia, animal ownership is very prevalent, and was integral to the wealth index. A short list of variables, common to both urban and rural areas, are iteratively selected to find those which result in high agreement (kappa>=0.75) against the original wealth index quintiles for national and urban populations. For Tunisia, the scores for urban and rural residents were combined into a national score using linear regression, in a process similar to that used by UNICEF. Specifically, a score from the simplified index for urban residents (Uscore) was regressed against the wealth index score variable created for the recreated 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
Nscore=b2Rscore + a2
Where Urban=1 if respondent lives in urban area and 0 if otherwise, and Rural =1 if respondent lives in 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 137 variables using the kappa statistic.
The questions in the simplified index which resulted from this process differ from our standard approach. We need to know whether the respondent lives in an urban or rural area. An additional question was added to the EquityTool: '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 Tunisia MICS 2018. In reality, 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 what 'urban' and 'rural' is.
- Allow the data collector to determine, based on guidance provided. This will work best if 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 2nd quintiles (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 MICS. 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 wealth index.
The graph below illustrates the difference between the EquityTool generated index and the full wealth index. Among all of those people (20% of the population) originally identified as being in the poorest quintile, approximately 85% are still identified as being in the poorest quintile when we use the simplified index. However, approximately 12% 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 12 questions produces results that are not identical to using all 42 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 wealth index:
|EquityTool National Quintiles|
|Quintile 1||Quintile 2||Quintile 3||Quintile 4||Quintile 5||Total|
|Original National Quintiles||Quintile 1||17.58||2.40||0.01||0.00||0.01||20.01%|
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||17.35||2.41||0.20||0.01||0.04||20.0%|
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 0.2% of people in Tunisia live below $1.90/day, and 0.6% live below $3.20/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 Tunisia, 26% of people living in urban areas are in the richest national quintile, compared to only 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 Tunisia 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 car dealership, 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 email@example.com and we will assist you.
 From povertydata.worldbank.org, reporting Poverty headcount ratio at $1.90/day at 2011 international prices.
 From the Tunisia MICS 2018 dataset, available at https://mics.unicef.org/surveys