The extent and quality of the statistics available varies from country to country. Every care has been taken to specify the broad definitions on which the data are based and to indicate cases where data quality or technical difficulties are such that interpretation of the figures is likely to be seriously affected. Nevertheless, figures from individual countries may differ from standard international statistical definitions. The term “country” can also refer to territories or economic entities.

Definitions of the statistics shown are given on the relevant page or in the glossary. Figures may not add exactly to totals, or percentages to 100, because of rounding or, in the case of GDP, statistical adjustment. Sums of money have generally been converted to US dollar sat the official exchange rate ruling at the time to which the figures refer.

Some country definitions
Macedonia is officially known as the Former Yugoslav Republic of Macedonia. Data for Cyprus normally refer to Greek Cyprus only. Data for China do not include Hong Kong or Macau. For countries such as Morocco they exclude disputed areas. Congo-Kinshasa refers to the Democratic Republic of Congo, formerly known as Zaire. Congo-Brazzaville refers to the other Congo.

Euro area data normally refer to the 19 members that had adopted the euro as at December 31 2017: Austria, Belgium, Cyprus, Estonia, France, Finland, Germany, Greece, Ireland, Italy,  Latvia, Lithuania, Luxembourg, Malta, Netherlands, Portugal, Slovakia, Slovenia and Spain. Euro area (16) refers to the 16 countries in the Euro Area that are members of the OECD. Data referring to the European Union include the UK, which in June 2016 voted in a referendum to leave the EU. Negotiations over the country’s are due to run until 2019. For more information about the EU, euro area and OECD see the glossary.

Statistical basis
The all-important factor in a compilation of this kind is to be able to make reliable comparisons between countries. Although this is never quite possible for the reasons stated above, the best route, which this publication takes, is to compare data for the same year or period and to use actual, not estimated, figures wherever possible. In some cases, only OECD members are considered. Where a country’s data are excessively out of date, it is excluded. The research for this edition of The Economist World in Figures was carried out in 2018 using the latest available sources that present data on an internationally comparable basis.

Other definitions
Statistics for principal exports and principal imports are normally based on customs statistics. These are generally compiled on different definitions to the visible exports and imports figures shown in the balance of payments section. Energy-consumption data are not always reliable, particularly for the major oil producing countries; consumption per person data may therefore be higher than in reality. Energy exports can exceed production and imports can exceed consumption if transit operations distort trade data or oil is imported for refining and re-exported.