Most of the data presented in these annexes refer to the school year 2002/2003, and are based on survey results reported to and processed by the UNESCO Institute for Statistics (UIS) before the end of May 2005. They are supplemented by statistics from other international organizations, including the United Nations Development Programme (UNDP), the United Nations Population Division (UNPD) and the World Bank.
A total of 203 countries and territories are listed. Most of them report their data to UIS using standard questionnaires. For some countries, however, education data are collected under the auspices of the World Education Indicators (WEI) project funded by the World Bank, or are provided by the Organisation for Economic Co-operation and Development (OECD) and the Statistical Office of the European Communities (Eurostat).
Education data reported to UIS are in conformity with the 1997 revision of the International Standard Classification of Education (ISCED). ISCED is used to harmonize data and introduce more international comparability among national education systems, but some countries may have their own definitions of education levels that do not correspond to ISCED.