A base year refers to the base point in time of a time series such as with a GDP deflator to convert GDP at current market prices into GDP at constant prices.
The reliability of GDP data is distorted by the failure of countries to regularly update their base years.
When GDP is revised and the base year is updated, it allows the statistician to reweight the relative importance of the different sectors of economic activity, and further change or reconsider the methods and data sources.
Note: The China Base Year listed has been used for official GDP up to the end of 2025, from 2026 China has moved to a new base year of 2025. Official GDP data prior to 2026 may take a few months to be retroactively updated to the new base year.
Data source: World Economics Research, London