i. Central statistical agencies ii. Historical reconstructions iii. Estimates iv. Conjectures Virtually all benchmark data after 1960 (i.e. 1960, 1970, 1980, 1990, 2000, and 2010) are derived indirectly from Central Statistical Agencies and therefore probably better classify as historical reconstructions. The remaining data are estimates

General references

The data were derived by combining two main datasets. First, Morrisson and Murtin (2009) supply information of around 78 countries for 10-year intervals. Second,Van Leeuwen, Van Leeuwen-Li and Foldvari, has been published in a range of papers spread over the past years (e.g. Van Leeuwen and Foldvari, 2008a; Foldvari et al., forthcoming) and has been made available in a comprehensive format by Clio-Infra in 2012. The last two datasets, from Van Leeuwen et al. and Morrisson and Murtin, have been shown to be the ones with the widest coverage, the longest time span and the highest reliability (e.g. Foldvari et al., forthcoming). The methodology for the two is also roughly comparable, making it possible to combine the two sets of estimates into a single comprehensive dataset on educational development.

The main sources, with the exception of some country-specific studies, are:

* Mitchell, B.R. (2007), International Historical Statistics: Africa, Asia & Oceania, 1750-2005, Basingstroke [etc.]: Palgrave Macmillan (5th edition).

* Mitchell, B.R. (2007), International Historical Statistics: The Americas, 1750-2005, Basingstroke [etc.]: Palgrave Macmillan (5th edition).

* Mitchell, B.R. (2007), International Historical Statistics: Europe, 1750-2005, Basingstroke [etc.]: Palgrave Macmillan (5th edition).

* US Department of Commerce, US Census Bureau, International database, downloaded from: http://www.census.gov/population/international/data/idb/informationGateway.php

* Unesco, Statistical yearbook, Paris: Unesco, 1964-1999, 1963-1999

* Blue books of the British colonies (various issues)

Some of the data are also taken from papers:

* Morrisson, Ch, and F. Murtin (2009), "The Century of Education," Journal of Human Capital, Vol. 3/1, pp. 1-42.

* Földvári, P., and B. Van Leeuwen, (2009), "Average years of education in Hungary: annual estimates 1920-2006," Eastern European Economics, Vol. 47/2, pp. 5-20.

* Földvári, P., B. Van Leeuwen, and J. Van Leeuwen-Li (forthcoming), "Educational and income inequality in Europe, 1870-2000," Cliometrica, Forthcoming.

* Leeuwen, Bas van, Jieli van Leeuwen-Li, and Péter Földvári, 'Regional human capital in Republican and New China: Its spread, quality and effects on economic growth,' 26 July 2011.

* Leeuwen, Bas van, Jieli van Leeuwen-Li, and Péter Földvári, 'Was education a driver of economic development in Africa? Inequality and income in the twentieth century,' 23 April 2012.

* Dmitry Didenko, Péter Földvári and Bas van Leeuwen, 'The spread of human capital in the former Soviet Union area in a comparative perspective: Exploring a new dataset,' Journal of Eurasian studies, Vol. 4 (2) 2013, pp. 123-135.

In 2010, the Netherlands Organisation for Scientific Research (NWO) awarded a subsidy to the Clio Infra project, of which Jan Luiten van Zanden was the main applicant and which is hosted by the International Institute of Social History (IISH). Clio Infra has set up a number of interconnected databases containing worldwide data on social, economic, and institutional indicators for the past five centuries, with special attention to the past 200 years. These indicators allow research into long-term development of worldwide economic growth and inequality.

Global inequality is one of the key problems of the contemporary world. Some countries have (recently) become wealthy, other countries have remained poor. New theoretical developments in economics - such as new institutional economics, new economic geography, and new growth theory - and the rise of global economic and social history require such processes to be studied on a worldwide scale. Clio Infra provides datasets for the most important indicators. Economic and social historians from around the world have been working together in thematic collaboratories, in order to collect and share their knowledge concerning the relevant indicators of economic performance and its causes. The collected data have been standardized, harmonized, and stored for future use. New indicators to study inequality have been developed. The datasets are accessible through the Clio Infra portal which also offers possibilities for visualization of the data. Clio Infra offers the opportunity to greatly enhance our understanding of the origins, causes and character of the process of global inequality.