This visualisation uses the country-level Human Development Index (HDI) data published by the United Nations Development Programme and population data from the World Bank’s World Development Indicators. The HDI reflects health, education, and income levels across countries and over time.
The chart is an interpretation of the data because the data is not represented precisely. The value of the HDI for each country has been moved a small random amount, both horizontally and vertically, and these ‘jittered’ values are used to produce the chart. The jittering is done in your browser before the chart is displayed, so each time the chart is viewed it will have some subtle differences, but the overall patterns will be the same.
Each dot in the chart represents a fixed number of people in a single country. These have been rounded to the number of people shown in the chart’s legend. This number changes depending on the size and resolution of your screen – if you view it on a larger or better quality screen the number of people per dot will reduce.
Rounding of country populations is done in a probabalistic way so that small countries are still represented. For example, if the scale is 10 million people per dot then standard rounding would result in no dots being drawn for all countries with populations less than 5 million. With probabalistic rounding, in this example there is a 40% chance that a dot is drawn for a country with a population of 4 million, in each year. This results in an approximate representation of small countries, and the random nature of this rounding also means that the chart will be slightly different each time it is vieweed.