The SNB equates price stability with a rise in the national consumer price index (CPI) of less than 2% per annum. In so doing, it takes into consideration the fact that not every price increase is necessarily inflationary, and that inflation cannot be measured accurately. Measurement problems arise, for example, when the quality of goods and services improves. Such changes are not fully taken into account in the CPI calculation; as a result, measured inflation tends to be slightly overstated.