Today’s CPI release from the CSO reports that the headline rate of annual inflation rose from 2.8% in October to 2.9% in November. As has been the case since inflation returned to positive territory in the middle of 2010 this continues to be mainly driven by just two categories; energy products and mortgage interest.
The price of energy products are up 13.7% in the year, while the price of mortgage interest is up 17.8% in the year. These make up 15% of the index and removing them gives a measure of ‘core’ inflation. Core annual inflation in November was 0.66%, up from 0.55% in October.
On mortgage interest, it is important to realise that the CPI measures the price of mortgage interest and not necessarily the cost. The price of mortgage interest change but the cost to most households may not change if this change is not also applied to existing mortgages. This has happened in Ireland for the past 18 months or so. Mortgage variable rates have been increasing far more than tracker rates and these form most of the mortgage interest price in the CPI.
The mortgage inflation rate in the CPI overstates the average increase in mortgage rates as it reflects mainly the rates that have been rising by more(standard variable rates) and largely omits the rates which rose only slightly (tracker rates). Almost half of all mortgages are on tracker rates. This is explained in a Information Note to the CPI release.
In line with normal practice for a fixed base price index, the current approach to measuring mortgage interest in the CPI reflects the situation in the base reference period December 2006 when the standard variable rate was dominant. Subsequently, tracker mortgages have become more popular. This did not give rise to any difficulties while the standard variable and tracker mortgage interest rates moved broadly in line with one another, which would be the normal expectation. However, the decoupling that has taken place since August 2009 has resulted in dramatically different trends emerging. For example, between September 2009 and September 2010 the standard variable rate increased from 2.93% to 3.66% whereas the tracker rate did not change. The Mortgage Interest component of the CPI, which is largely determined by the trend in the standard variable rate, increased by 25.1% as a result and contributed +1.25% to the overall change in the All Items index. It is crudely estimated that the latter impact would have been reduced by between 0.2% and 0.5% had the Mortgage Interest component been calculated on a current weighting basis. Users should take this “weighting effect” into account in interpreting the mortgage interest related movements in the index.