Simplified Asset Indices to Measure Wealth and Equity in Health Programs: a Reliability and Validity Analysis Using Survey Data from 16 Countries

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Background: Social franchising programs in low- and middle- income countries have tried using the standard wealth index, based on the Demographic and Health Survey (DHS) questionnaire, in client exit interviews to assess clients’ relative wealth compared with the national wealth distribution to ensure equity in service delivery. The large number of survey questions required to capture the wealth index variables have proved cumbersome for programs.

Methods: Using an adaptation of the Delphi method, we developed shortened wealth indices and in February 2015 consulted 15 stakeholders in equity management. Together, we selected the best of 5 alternative indices, accompanied by 2 measures of agreement comparing wealth quintile assignment in the new indices to the full DHS text. The panel agreed that reducing the number of assets was more important than standardization across countries because a short index would provide strong indication of client wealth and be easier to collect and use in the field. Additionally, the panel agreed that the simplified index should be highly correlated with the DHS for each country for both national and urban-specific examples. We then revised indices for 16 countries and selected the minimum number of questions and question options required to achieve a kappa statistic greater than or equal to 0.75 for both national and urban populations.

Findings: After combining the 5 wealth quintiles into 3 groups, which the expert panel deemed more programmatically meaningful, reliability between the standard DHS wealth index and each of 3 simplified indices was high. Index E was the simplified index of choice because it was reliable in national and urban contexts while requiring the fewest number of survey questions- 6 to 18 per country compared with 25 to 47 in the original DHS wealth index.

Conclusion: Social franchise clients and other types of service delivery programs that want to assess client wealth in relation to a national or urban population can do so with high reliability using a short questionnaire. Future uses of the simplified asset questionnaire include a mobile application for rapid data collection and analysis.