Most data for series in the UK Data Service macro data collection are produced by national statistical offices under the standards set by the UN and other IGOs (see earlier section). But it is not always reasonable for countries to work to the same standard; less rich economies may not wish to use as many resources as rich countries to produce statistics. So a common standard and hence complete comparability is not yet possible. Furthermore, there is often more than one reasonable definition for a data series, and more than one methodology for calculating it. So series for different countries are not necessarily exactly comparable. The OECD, Eurostat and World Bank have produced guidelines for comparability. They also manage programmes to produce comparable series (see later section). Nonetheless in making cross national comparisons, it is often important to check definitions and methodologies

Information on data series, including accounting conventions, classifications, definitions, descriptions, and methodologies is often called metadata. Included are characteristics such as periodicity (annual, quarterly monthly etc.), geographical area or political state for which the data have been collected, timing of measurement (e,g, whether a 'stock' series is valued at start, middle or end of accounting period), base years, units etc.. Details of series breaks (for example following a refinement of definition) and any recalculations of past data based on the post-break conventions are part of metadata.

Information required by quality protocols, including contact, publisher, publication dates, original source, code number etc. is also metadata

Much metadata is published alongside the data, within the same tables.