B40 Dashboard

As affordable housing investors across Africa seek to extend the market to lower income households, an understanding of the poorest 40% of a country’s population – the bottom 40% or B40, has become an important consideration. This dashboard uses data from the Demographic and Health Surveys (available here) to profile B40 households across Africa. This dashboard is intended to support investors’, policy makers’ and other housing sector practitioners’ understanding of the B40. However, it does not provide all the answers so please use the comments section at the bottom of the page to make suggestions or ask additional questions.

This dashboard contains data from ten African countries, organised into 5 groups of indicators calculated at the national, urban, and city level. These indicators can be viewed in three different ways:

  • Compare B40 across countries compares the B40 groups of up to four countries at once for a broader view of the state of the B40 across Africa
  • Compare by wealth segment compares the B40 with the wealth segments Middle 40% (M40) and Top 20% (T20) for one country at a time, allowing for greater analysis of within-country dynamics
  • Compare by housing situation identifies and calculates indicators for different groups within the entire population of households based on salient dwelling characteristics for one country at a time, for a closer look into specific housing issues

Where applicable, hover over an information icon attached to an indicator or section to read more details. Click here for further instructions on how to use this dashboard and additional information.

Data source: ICF. 2011-2019. Demographic and Health Surveys (various) [Datasets]. Funded by USAID. Rockville, Maryland: ICF [Distributor].

Click here for a full list of indicator definitions used in the dashboard.

About the data

The DHS Program

The Demographic and Health Surveys (DHS) are the flagship product of the Demographic and Health Surveys Program, a project funded by USAID with the aim of increasing visibility of issues in the developing world. Today, DHS Program has conducted surveys in more than 90 countries. DHS surveys are typically conducted in collaboration with national statistics bureaus. The DHS uses a standardised questionnaire, which makes it an excellent tool for cross-country comparisons. Access the DHS Data here.

Developed by 71point4

Commissioned by Centre for Affordable Housing Finance in Africa

Funded by FSDAfrica and UKAID


About the Bottom 40%

What and why the Bottom 40%?

The Bottom 40% (B40) refers to the poorest 40% of a given population. The World Bank has in recent years popularised the Bottom 40% as a specific market of focus. Its shared prosperity objective aims to “foster the income growth of the bottom 40 percent of the population in every country”. Since the 1990 World Development Report on poverty, various World Bank Group flagship studies and strategy documents have recognized that high levels of inequality can be an obstacle to sustained poverty reduction. In some case studies, the World Bank goes as far as to state that the 2030 vision is for B40 income growth to be sustained at levels greater than the growth of average household income. Should that target be achieved, a decrease in inequality will follow. This itself is a component of United Nations Sustainable Development Goal #10: “Reduce inequality within and among countries”.

Construction of B40 within each geographic segment

The B40 is identified using a wealth index, which uses information on household and personal assets owned to create a ranking of individuals. The B40 can be identified by arranging these individuals from least wealthy to most wealthy, and selecting those who make up the lowest 40% of this ordering. These individuals are called B40 individuals, and the households they live in are B40 households. The ranking is calculated in such a way that all members of a household will fall into the same wealth level. For the sake of context, also referenced in this dashboard are the Middle 40% (M40) and Top 20% (T20), which are identified the same way.

In this dashboard, the wealth rankings are recalculated for each geographic level. The national B40 is defined on the total national population, but only the urban population is used to define the urban B40, and only the population of the largest city is used to define the largest city B40. Therefore the sample for the national B40 is the poorest 40% of all individuals and their households, the sample for the urban B40 is the poorest 40% of all urban individuals and their households, and the sample for the largest city B40 is the poorest 40% of all largest city individuals and their households. The samples for M40 and T20 should be interpreted similarly. This recalculation is necessary due to the significant differentials in average wealth national, urban, and largest city areas: typically, wealth levels are higher in urban areas than they are nationally, and higher still in the largest city. If only the national wealth ranking was used throughout the dashboard, the B40 sample would be too small to conduct reliable analysis at the urban and largest city levels.

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