> I’d argue “2001 dollars” is a unit, Why though? Why dollars in a particular year, rather than dollars in general? Sure the value of a dollar changes from y

> I’d argue “2001 dollars” is a unit, Why though? Why dollars in a particular year, rather than dollars in general? Sure the value of a dollar changes from year to year, but the value of a dollar also changes constantly in any given year too. Over the past year, the value of a US dollar relative to a Euro has fluctuated by more than 10 cents. In fact the relative values of currencies fluctuate constantly, near-enough to instantaneously. But this isn't reflected in the pricing of most consumer goods; the price of common household goods in a grocery store might vary a few times a week, but not thousands of times an hour. So in one context the value of a dollar seems to vary constantly, but in another context the value of a dollar is substantially more stable. So a dollar doesn't even have a set particular value at any instant in time; it depends on what kind of store you're standing in. If happiness is a metric with units even worse than this, then I see little hope for any scientific study of happiness.