In making cross-national comparisons it is obviously important that a data series from one country should be measuring the same characteristics as the same series from another country. However since data from each country originates from that country's own statistical department there is a danger that this won't be the case. To minimise this danger, IGOs (intergovernmental organisations) have for a number of years sought to develop common frameworks for definitions, locations, time periods, methodologies and accounting principles for a vast range of data series.

The United Nations Statistical Commission created and now oversees the implementation, publication and revision of a common framework for national accounts. It does so in collaboration with four other IGOs Euro-Stat, IMF, OECD and World Bank under the auspices of the Inter-Secretariat Working Group on National Accounts (ISWGNA). This group convenes and takes advice from expert working parties on various issues and publishes SNA News and Notes. Recommendations on these matters are made to the UN Statistical Commission whose views are given international legal force through endorsement by the UN.

The framework for national accounts created by the UN is often referred to as the 1993 United Nations System of National Accounts or SNA(93). At present (2006) the system is being revised. Occasionally the pre- 1993 framework is used, referred to by its year of origin, 1968, e.g. 1968 SNA.

Euro-stat has produced its own version of SNA(93), often referred to as the European System of Accounts - ESA 95, to gain even more precise commonality across European national accounts. The previous European framework is referred to as ESA 79. In general ESA 95 data series are compatible with 1993 SNA series.

More disaggregated economic data, social, health and education data is produced by the statistical departments of all countries. To make cross country comparisons using this data requires a common classification framework. This is provided by the UN Statistical Commission or, for their own specialised fields, the World Customs Organisation (WCO), World Health Organisation (WHO), IMF and International Labour Organisation (ILO). The UNSC provide a good explanation of basic principles.

Many ESDS International macro-databanks series are based on the ISIC (International Standard of Industrial Classification of All Economic Activities) classification. This characterises all economic activity into groups and levels based on type of activity. For example at the highest level, it uses the category 'Manufacturing', but disaggregates to sub-classes such as 'Manufacture of electric motors, generators and transformers' and sometimes to even finer levels.

ESDS International provides a users guide to this. The UN Statistics Division provides more details of ISIC classifications including ISIC Revision 3 and ISIC Revision 3.1 . This year, a new revision of ISIC has now been approved by the UNSC, ISIC Revision 4 . However it is too early for this to be in general use.

Most series for most countries will be ISIC revision 3 or .3.1, but some data series classified under earlier revisions are still current.

Other similar classifications schemes exist for particular purposes.

ESDS international data-banks contain series on energy, oil and related matters produced by the Energy Statistics Division of the International Energy Authority (IEA) (see ESDS International Dataset User Guide: International Energy Databases).

The IEA which, originated from OECD and Euro-stat, compiles energy statistics from questionnaires, completed by national statistics offices. It thus seeks spatially harmonised statistics.

The IEA's definitions and methodologies are obtainable from ESDS International databanks as 'Documents'.

Example 1: Obtaining definitions and methodologies

For example select 'IEA data' from the ESDS International home page then click 'World Energy Statistics'. The report screen looks as below:

Most IEA "Beyond 20/20" pages will have such a sub-folder tab. The documentation, amongst other things will have sections on scope and methodology and comparability.

The World Bank is seeking to harmonise many non-economic data series. For details to check comparability see notes attached to World Bank series on the ESDS International 'Report page' or 'Beyond 20/20 data tables' and look at 'Definitions' of 'Population and Demographic Indicators' and 'Education Health and Poverty Indicators' on the World Bank Data and Statistics overview.