One of the most useful things you can do in debate is reveal yourself to be immune to evidence of anything you don't like. It is useful because it allows rational participants to stop wasting time with you.
The data says people are saying they are less happy over some time period. There are 2 competing hypotheses to explain the cause.
1) Society has changed in a way that has made people less happy. 2) Society has changed in a way that has made people less likely to lie about being happy.
If you stop to think it through for a second, you’ll quickly understand how the statement “we have some data from somewhere in the middle of the time period in question that self reported satisfaction and a actual satisfaction are correlated” isn’t evidence to support either side. That statement can easily fit either hypothesis.
This is quite easy to test in a longitudinal cross-cultural study of people over time. You'd probably find half a book shelf of research already which does exactly that, if only one bothered to look for it.
