Abstract: In societies where, comprehensive free public services are provided and where the after-tax income grows synchronously with the productivity growth, the merchandise ( including material merchandise and service merchandise and assets merchandise) price index will systematically deviate from the welfare price index and from real purchasing power of money index, i. e. the merchandise price index will be higher than the welfare price index. I suggest labeling the gap between the merchandise price index and the welfare price index as “Public Service Deflator”. By detracting the Public Service Deflator, we can eliminate the exaggeration intrinsic in the merchandise price index, and thus make accurate assessment of monetary condition and form appropriate attitude towards the so-called inflation or deflation as presently defined.