New reference year, 2015=100, in the Consumer Price Index (CPI)


From the 10. of February 2017, the reference year in the CPI has changed to 2015. The previous series with 1998=100 will no longer be updated. Also the reference year for CPI adjusted for tax changes (CPI-AT) and CPI adjusted for tax changes and excluding energy products (CPI-ATE) and other derived series are changed to 2015 as of the 10. of February.

In the period August 1999 to December 2016, 1998=100 is the official CPI.

CPI aggregated to consumer groups is recalculated back to January 1979. Other series are recalculated back to the start of the different series. The CPI all item index is recalculated back to 1865 on a yearly basis and to 1920 on a monthly basis. 

Statistics Norway follows earlier principles to publish the CPI with only one decimal. Monthly and year-to-year changes are recalculated based on new index levels with 2015=100 and rounded to one decimal for publication. Also changes in the annual indices follow this principle. Published rates of change will therefore correspond with published index levels. It is especially important to be aware that changed reference year will give differences in already published rates of change. This means that rates of change calculated from 2015=100 series can be different from rates of change calculated with 1998=100. This is due to rounding effects. Change of reference year has no effect on the annual growth rate in the CPI for2016, which was 3.6 per cent. However there are some differences in the year-to year growth rates of 2016. 

There has been a price growth in the period 1998 to 2015 and changing the reference year will give an index series with lower index levels. Due to index levels published with one decimal, rates of change with 2015 =100 will be exposed to relatively higher rounding effects than change rates calculated from 1998=100. For price changes based on annual indices there can be significant deviations from published rates of change with 1998=100, the deviations are however not systematical.

If you have any questions concerning the new reference year, contact konsumprisindeksen@ssb.no.