Usually European countries would use the HICP: https://en.wikipedia.org/wiki/Harmonised_Index_of_Consumer_Prices https://en.wikipedia.org/wiki/Harmonised_Index

Usually European countries would use the HICP: https://en.wikipedia.org/wiki/Harmonised_Index_of_Consumer_Prices https://en.wikipedia.org/wiki/Harmonised_Index_of_Consumer_P... This ought to ensure inflation rates are at least comparable on some level between countries.