The reference is the sample used for the survey. Select a different sample and you get an entirely different result. It depends on not just what cost of living

The reference is the sample used for the survey. Select a different sample and you get an entirely different result. It depends on not just what cost of living is but how much your friends and neighbors make. From this result alone you'd conclude that medieval people lived in utter despair, but I'm pretty sure that was not the case. So it's kind of pointless.