Abstract This review is the introduction to a special issue of Economic Systems Research on the topic of global multiregional input–output (GMRIO) tables, models, and analysis. It provides a short historical context of GMRIO development and its applications (many of which deal with environmental extensions) and presents the rationale for the major database projects presented in this special issue. Then the six papers are briefly introduced. This is followed by a concluding comparison of the characteristics of the main GMRIO databases developed thus far and an outlook of potential further developments. Keywords: Multiregional input–output tablesGlobal analysisEnvironmental extensionsTradeSupply and use tables Acknowledgements We would like to thank Satoshi Inomata, Manfred Lenzen, Bart Los, Glen P. Peters, Terrie Walmsley, and Thomas Wiedmann for their comments on an earlier version of this editorial introduction. Notes 1The projects discussed in this special issue are also portrayed in Murray and Lenzen Citation(2013), a forthcoming popular-scientific book on MRIO. 2See http://www.oecd.org/sti/inputoutput 3Another example is the series of tables, constructed by researchers from the University of Groningen, for a set of European countries. The full series of intercountry tables in current prices (for the years 1965, 1970, 1975, 1980, and 1985) can be downloaded at http://www.regroningen.nl. The details of the construction method are given in van der Linden Citation(1999), a summary is given by van der Linden and Oosterhaven Citation(1995). For the intercountry tables in constant prices, see Hoen Citation(2002). 4The Réunion Project (http://www.isa.org.usyd.edu.au/mrio/mrio.shtml) is aimed at linking the top global institutions involved in the compilation of GMRIO accounts, and at initiating a large-scale research collaboration that will be able to harmonize world-wide activities on GMRIO database compilation. The idea for this collaboration originated from a meeting of the present researchers at the 18th Input–Output Conference held in 2010 at the University of Sydney. 5EXIOPOL is the acronym of an EU funded project called ‘A new environmentally accounting framework using externality data and input output tools for policy analysis’. 6Available at: http://trade.ec.europa.eu/doclib/docs/2012/april/tradoc_149337.pdf. 7See http://www.un.org/esa/analysis/link, or, e.g. Moriguchi Citation(1973) and Klein Citation(1985). 8The countries covered in the international systems are Austria, Belgium, Canada, China, France, Germany, Italy, Japan, Mexico, South Korea, Spain, the United Kingdom, and the United States. The two regions cover the rest of Europe and the rest of the world. See http://inforum.umd.edu, or, e.g. Almon Citation(1991) and Nyhus Citation(1991). 9Examples are emission data in most countries (which, if available at all, do usually not adopt the same sector classification as applied in the SUTs or IOTs), the countries of origin of imports (which are usually not given in national SUTs/IOTs), differences between trade data in SUTs/IOTs and in the trade statistics, imbalances in trade data (i.e. imports from country X reported by country Y do not equal the reported exports by country X to country Y), differences between countries in the type of SUT/IOT that they compile (e.g. some publish SUTs, other IOTs, which can be of the industry-by-industry or the product-by-product type), valuation differences (e.g. producer's, purchaser's and basic prices), differences in sector and product classifications. 10For instance, Wiedmann et al. Citation(2011) express the hope that the so-called ‘Group of Four’ in the EU (EU DG ENV, Eurostat, EEA, and DG JRC) could be a vehicle for GMRIO development initiated by Europe. For practical purposes, it is in the meantime unclear whether the Go4 will remain active in the future. Another experience is that in a project for Eurostat it proved to be impossible to create even an MRIO table for the EU27 countries due to confidentiality problems, so that eventually an aggregated EU27 EE IOT was constructed (e.g. Eurostat, Citation2011; Tukker et al., 2012). 11This special issue has papers on all databases in Table 1, with the exception of GRAM. 12Indeed, we would claim that the ‘extensions embodied in trade’ (EEBT) approach is inferior. It uses national EE IOTs to calculate, for example, the pollution in country A as embodied in its exports to country B (and country C, and so forth). In the same fashion, country A also imports pollution embodied in its imports from country B (and country C, and so forth). The answers from this EEBT approach will differ from those obtained from applying a GMRIO table. A simple example suffices to show why. It may be the case that countries A and B do not trade with each other (in which case the EEBT approach will report no pollution embodied in their trade). However, it may happen that all trade between A and B goes through a third country C. Using a GMRIO model will in that case report positive imports and exports of pollution between countries A and B. 13Although this appears to be obvious, it is less simple than it seems. SUTs and IOTs reflect sales and use of fossil fuels. Many EE MRIO databases use the IEA database, where energy is allocated to the sector of use, and emission factors to calculate emissions. If such ‘IEA-based’ emissions are replaced by emissions of external databases like EDGAR, one may end up in a situation where, e.g. CO2 emissions do not match, e.g. the IEA fuel use for an industry. The databases that use IEA energy flow data to calculate emissions, may use physical energy uses that are not consistent with the economic data in the SUT/IOT. 14Current work in progress on incorporating sub-national regions into a GMRIO includes Cherubini and Los Citation(2012) on Italy, Dietzenbacher et al. Citation(2012a) on Brazil, and Inomata and Meng Citation(2013) on China-Japan-Korea. 15See www.creea.eu, accessed 12 August 2012. 16For instance, Eco-invent, one of the dominant LCI databases, is currently organizing its data as a supply use system. Personal communication with Eco-invent staff also suggests they may want to move to using product and sector codes usually applied in economic statistics, as well as encouraging data providers to supply (next to the traditional physical information) also price information on inputs and outputs. See, e.g. http://www.ecoinvent.org/df-lca-ecoinvent-v3/, accessed 12 August 2012.