Why the latest official UK inflation figures are not what they seem

Official data suggests the UK’s rate of inflation eased from 3.5% in April to 3.4% in May – but in reality the figure was unchanged, standing at 3.4% in both months.

The discrepancy is to do with an error made in the initial calculation of April’s inflation rate.

When April’s Consumer Prices Index figure was first reported by the Office for National Statistics (ONS), on May 21, it was stated as being 3.5%.

However on June 5, the ONS issued a statement saying this figure was incorrect and that it should have been 3.4%.

The ONS said it had spotted a mistake in the way April’s rate had been calculated.

The error was to do with data from the Department for Transport concerning vehicle excise duty (VED).

This data had overstated the number of vehicles subject to VED – which in turn led to the ONS overstating April’s overall rate of inflation by 0.1 percentage points, reporting it to be 3.5% instead of 3.4%.

But while April’s rate is now known to have been wrong, the ONS has a policy of not revising official inflation figures in subsequent publications.

This is why, in the inflation data published on Wednesday, the ONS said April’s inflation rate was 3.5%, not 3.4% – and why its figures suggest inflation eased month on month, instead of what actually happened, which is that it remained at 3.4%.

April’s inflation figure will continue to be stated by the ONS as 3.5%, despite it actually being 3.4%.