Documentation — version 27
Summary documentation of v27
GDP per capita measures the value of everything produced in a country during a year, divided by the number of people. The unit is in international dollars, fixed to 2017 prices. The data is adjusted for inflation and differences in the cost of living between countries, known as PPP dollars.
In more recent years, between 1990 and 2019, we use the GDP per capita data from the World Bank, published in March 2021 in their World Development Indicators. Before the World Bank series starts in 1990, we have used several sources:
Maddison Project Database: The Maddison Project was started in March 2010 by a group of Angus Maddison’s close colleagues, with the aim of supporting an effective cooperation between scholars to continue Maddison’s work on measuring economic performance for different regions, time periods and subtopics. The MPD built on Maddison’s original dataset. The original estimates are kept intact, and only revised or adjusted when there is more and better information available. Currently, the database is maintained and improved by the Groningen Growth and Development Centre.We have used the data in their 2020 version which provides information on comparative economic growth and income levels over a very long period. The 2020 version covers 169 countries and the period up to 2018.
Penn World Table: We use data from the Penn World Table version 10.0 of the Groningen Growth and Development Centre, which is a platform for research on economic growth and development. PWT version 10.0 is a database with information on relative levels of income, output, input, and productivity, covering 13 countries between 1950 and 2019.
Gapminder v26: This is the previous version of GDP per capita published by Gapminder, and which was based on World Bank, IMF, and historical time series from the Maddison Database Project 2018 version, PWT 9.1 and GM-GDP per Capita v14 (documented and detailed based on multiple sources but mostly based on Agnus Maddison). For more details on previous versions, see the documentations below. We use GM-GDP per Capita v26 for the historical time series which are not available in the Maddison Project database or Penn World Table.
How were the sources combined?
We first updated our historical estimates based on the new data released by the Maddison Project Database (MPD) and Penn World Table (PWT). We used MPD data wherever data is available. Otherwise, we used PWT estimates.
In general, we connected Gapminder historical data in version 26 to MPD/ PWT data and adjusted the data based on the earliest available year with data in MPD or PWT. We made an exception for countries with MPD data available for the year 1820 or earlier, where we then used MPD data without any adjustment.
After, we connected the historical estimates to World Bank data by smoothly transitioning our historic trend over a period of 30 years to reach World Bank data for the first year it is available.
That describes the principle followed for most countries, but then we made exceptions in 31 cases where we preferred the following adjustments: (i) to use Gapminder’s series instead of MPD for the period 1800 to the start of WB data as the MPD data were mostly interpolated series and this makes events in single years not showing up as dips or peaks in single years. (ii) To move smoothly between GM/PWT and MPD in case the discrepancy between the estimates in the sources was large or (iii) To use MPD/PWT series instead of WB for some years.
Our data continues into the future up to 2026, based on forecasts from the IMF, in their World Economic Outlook 2021, April edition. We have applied the IMF expected changes rates on WB estimates. Beyond that point we have extended the series up to 2050. Economic forecasts are never very reliable, and we do these projections only to visualize an “if-then-scenario”. If the current trends for each country continued up to 2026, and if all countries at the end of the IMF’s forecast will converge to a common global (and modest) growth rate of 2% per year, then what would the world look like? Answering this question visually helps us show how much richer the world would become even with a modest growth rate. We’re not claiming that this is what will happen.
In some cases, the new estimates and forecasts made countries much richer than previous releases. This means that many countries moved their position in our bubble charts as the updated data changed drastically. For more details about the changes between versions, see a detailed data file for v27 here.
Detailed documentation and feedback
For transparency, we provide the files that we used to calculate this data, which can be found here. Any questions about the data and suggestions for how to improve it are always very welcome in our data forum.
(For several years we were too busy with other things, and failed to update this documentation. Many versions are simply missing from the list below, but those updates were quite trivial: We just kept updating the end of our long historic trends, with the latest numbers from the World Bank every time they released new data.)
» What was new in version 9 (word)
» Documentation of version 8 (pdf)
» Excel file with data and summary meta-data of version 8 (xlsx)
» Go to the google spreadsheet that contains the “data quality rates” for the indicator (spreadsheet)
» Download documentation of version 3 (pdf) – Version 3 is the version of the indicator before the major revision in 22 december 2008. The indicator is available in the graph, it is called “old version of income per person”