CPIH: The impact of adding housing to CPI

On the 21 March 2017, the UK will have a new headline inflation measure of CPIH. It is similar to the Consumer Prices Index (CPI) but attempts to add a measure of owner occupiers’ housing costs, hence the H.

In a separate post I have discussed the issues with this measure. In this one I want to specifically focus on the impact of adding housing to CPI. ONS have calculated what the CPIH rate would have been back to 2006. It is therefore possible to see whether it would have increased or decreased CPI. An initial look at the data suggests that sometimes one is higher, and sometimes the other. However looking more closely there is a strong correlation between the impact and the absolute level of CPI.

When CPI is low (below 2%), CPIH is usually higher than CPI. However when it is above the target 2% level, it usually adds to it. A simple correlation predicts that when CPI is 3%, CPIH may deduct nearly 0.3% from it. At 4% CPI, it could deduct 0.5%.

OOH scatterplot

The reason for this is that the Owner Occupiers’ Housing measure based on rents is a fairly stable number which has averaged just under 2%. Therefore when CPI is above that level, it acts as a drag on it downwards (and vice versa when CPI is below 2%).

Currently OOH is about 2.5%, but data from the Countryside Letting Index implies it will fall over the coming year. That is at the same time as the Bank of England is predicting that CPI will rise to nearly 3%. The net effect is likely to be that by this time next year, the new headline CPIH measure may well be 0.3% lower than had we stuck with CPI as the headline.