# Long definition
The **GDP implicit deflator** is calculated as the ratio of **GDP in current local currency** to **GDP in constant local currency**. This series has been **linked** to produce a **consistent time series** to counteract **breaks in series** over time due to changes in **base years**, source data and methodologies. Thus, it may not be comparable with other national accounts series in the database for historical years. The **base year** varies by country.
# Statistical concept and methodology
The accuracy of national accounts estimates and their comparability across countries depend on timely **revisions** to data on **GDP and its components**. The frequency of revisions to GDP data varies:
- some countries revise numbers **monthly**
- others **quarterly** or **annually**
- and others less frequently
Such revisions are usually small and based on additional information received during the year. However, larger revisions are required from time to time to **rebase** the national accounts and allow for incorporation of new methodologies and data sources.
Comprehensive revisions of GDP data often (but not always) result in **upward adjustments** to GDP and other major aggregates as improved data sources increase the coverage of the economy. And estimates of **GDP growth** may change as new weights are introduced. These revisions will cause **breaks in series** unless they are applied consistently to historical data. For **constant price series** a break caused by rebasing can be eliminated by **linking** the old series to the new using historical growth rates.
This **implicit GDP deflator series** has been **linked** to produce a consistent time series. It has been calculated by utilizing the change in the implicit GDP deflator in the **WDI Archive** and **IMF WEO** databases. Thus, earlier years (linked years) will not be comparable with other national accounts series in the database.
Data are available for **World Bank operational countries** only.