The information requested falls within the responsibility of the National Statistician, who has been asked to reply.
Letter from Karen Dunnell, dated 19 February 2008:
As National Statistician, I have been asked to reply to your Parliamentary Question asking what percentage of changes there were in a) the retail price index, b) the consumer price index, c) fuel prices and d) food prices in i) 2006, ii) 2007 and iii) 2008 to date. (186895)
In the table below I have provided the percentage changes over 12 months within a) the retail price index, b) the consumer price index, e) fuel prices and d) food prices.
2006 2007 January 2008 Consumer price index 2.3 2.3 2.2 Fuels and lubricants (CPI) 5.5 2.9 19.3 Food (CPI) 2.3 4.6 6.6 Retail price index 3.2 4.3 4.1 Petrol and oil (RPI) 5.5 2.7 19.0 Food (RPI) 2.1 4.6 6.6
The 2006 and 2007 figures provided are annual growth rates based on average prices in each calendar year. The January 2008 figures are the latest figures available (published on 12 February 2008), the table shows the percentage increase in prices between January 2007 and January 2008.
The CPI and RPI both measure the average change from month to month in the prices of consumer goods and services purchased in the UK. However, they differ in both coverage and methodology. A detailed description of these differences is given in an article entitled “The New Inflation Target: the Statistical Perspective”:
http://www.statistics.gov.uk/downloads/theme_economy/New_inflation_target_summary031210.pdf
Specifically when comparing petrol and oil (RPI) and fuels and lubricants (CPI), the major difference is the fact that the RPI measures pump prices on index day each month, whereas CPI measures the average pump price across the whole month.
The major difference between food in the RPI and CPI are the differences in the weights used to combine the low level indices.