Double Deflation Casts Doubt on Existing GDP Data

Brian Sturgess

Published: June 2017

Increasingly, national income statisticians, the specialists involved in producing real national income figures, and the users of those figures are living in a parallel universe. Most countries use an outdated and inaccurate method to estimate real Gross Domestic Product (GDP) by using what is termed single deflation. Best practice suggests using double deflation: one price index to deflate the prices of goods produced and another to deflate the value of intermediate goods used up in production. A recent study comparing single deflation calculations with double deflation official growth estimates for eight countries showed that, for some years, single deflation figures deviated up- or downwards from the official estimates by as much as 3–4 percentage points.