Since "happiness" by definition is subjective, how do you determine what the proxies to happiness are?
How do you correlate something to "happiness" (to determine its a proxy), if you can't measure happiness directly?
I mean, I agree that there's some significant problems in surveying a population, but I'm not aware of any other way to measure something subjective like happiness. I'd love to read the study you're referencing if you can find it.
It seems...like a really silly metric not to include in a quality of life ranking.