The data appearing in the World Economic Outlook are provided to the Research Department at the time of the WEO exercises. The historical data and projections are based on the information gathered by the IMF country desk officers in the context of their missions to IMF member countries and ongoing analysis of the evolving situation in each country. Historical data are updated on a continual basis as more information becomes available, and structural breaks in data are often adjusted to produce smooth series with the use of splicing and other techniques. IMF staff estimates continue to serve as proxies for historical series when complete information is unavailable.
The data published in the Statistics Department's International Financial Statistics (IFS) are gathered as part of an ongoing data collection effort in which member country statistical agencies provide public statistics to the IMF.
Data from the country source are updated on their own schedule. Each publication takes into account the most recent revisions available, prior to publication. The data provided in the WEO might have more (estimated) or less time coverage than what is provided by the authorities but that decision is at the discretion of the IMF country desk officers. For a specific country-series pair, the date (month and year) of the last update is indicated in the notes option you may choose to append to the report at the end of a query.
Because of differences in data collection techniques, methodological issues, focus, and timing, the data in the IFS, specified source and the World Economic Outlook may differ. Check our statement on revisions to the data and deviations from other official sources, such as IFS, here: http://www.imf.org/external/pubs/ft/weo/disclaim.htm.