Why does data sometimes change from year-to-year?

You may find that data for certain categories changes considerably from one year to the next. This is a result of either changed definitions or improved sources.

Very often, particularly in emerging markets, new sources become available that help our analysts refine their data estimates. Existing sources also change their "view" and reporting techniques meaning that even in developed markets we sometimes find it necessary to change data.

If you have any questions about year-on-year changes please speak to your account manager.