It is whatever you think is the most reliable way to measure increase/decrease in standard of living. That is what you base your decisions on. None of us pay official interest rates on our borrowings, and none of us can go to the supermarket and insist on paying only the official CPI increase on the price of our wheeties compared to last month.
Exactly. You must therefore agree that ym's assertion as he expressed it is not universally applicable. And by the way - what is the relevance of "standard of living" to ym's assertion? Goalposts again?