Personal anecdote, having lived in a few very poor countries and a few relatively very wealthy ones:

1) In the poor countries, I find people are generally quite happy living their day to day lives but rate their happiness low - because they think people in wealthy countries have it so much better. I.e. they underrate their happiness because they think wealthy people must be so much happier.

2) Vice versa in the wealthier countries - so many miserable people, but, they feel that they can't complain because they see how bad things are in the poor countries.

I think these "happiness ratings" are a bunch of bullshit. Some of the happiest families and communities I've seen are in the poor countries while so many people are miserable and lonely in the wealthy countries.

I believe it is very very hard for a person to subjectively rate their own happiness. (Edit to add, especially when they are comparing their own happiness against cultures and people they have mostly only seen on TV).