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In accordance with the Statistics and Registration Service Act 2007, the Retail Prices Index and its derivatives have been assessed against the Code of Practice for Official Statistics and found not to meet the required standard for designation as National Statistics. The full assessment report can be found on the UK Statistics Authority website.
The RPI is a long-standing measure of UK inflation that has historically been used for a wide range of purposes such as the indexation of pensions, rents and index-linked gilts. For further information see Users and uses of consumer price inflation statistics.
RPIJ is an improved variant of the Retail Prices Index, which is calculated using formulae that meet international standards. The rationale for creating RPIJ was to give users a better alternative to the RPI if their needs were for a measure of inflation based on the same population, classifications, weights etc as the RPI. Currently, RPIJ also acts as an analytical series in that it allows users to see the impact of using the Jevons (which meets international standards) in place of the Carli formula (which does not meet international standards) in the RPI. The use of the different formulae at the elementary aggregate level is currently the only difference between the two indices. ONS does not produce detailed goods and services indices for RPIJ.
In June 2014, the 12-month rate for RPIJ stood at 2.0%, up from 1.7% in May. CPIH and RPIJ broadly continue to track each other as they have done for the last two years.
The RPI 12-month rate for June 2014 stood at 2.6%, meaning that it was 0.6 percentage points higher than it would have been had it used formulae that meet international standards.
Figure D shows the RPI and RPIJ 12-month rates for the last 10 years. Over this period the RPIJ 12-month rate has been, on average, 0.5 percentage points lower than the RPI but the difference has increased to an average of 0.7 percentage points over the last 3 years. Cumulatively, inflation as measured by the RPI is 37.2% over the 10 year period, compared with 30.4% as measured by the RPIJ. The use of the Carli formula has therefore added 6.8 percentage points to the change in prices over the last 10 years.
Figure D: RPI and RPIJ 12-month rates for the last 10 years: June 2004 to June 2014