That measurement of 'happiness' is inappropriate. Instead of simply polling people about e.g. life satisfaction it's based on a bunch of random metrics that have, at best, a mixed relationship with 'happiness.'

So for instance it turns out the 'happiest' countries in the world also have some of the highest rates of depression in the world.

Now obviously that's not literally impossible but ffs just poll people - it's not hard. Yes it will be extremely subjective, exactly like 'happiness' is!