Most of these money go to investements that provide jobs for other people. There is an extra sense of satisfaction when one is an investor knowing that they provide wealth to others.

Sometimes, and usually only a fraction of it, but that is a whole other giant monster.

Still, they are in the US. The study is nonsense if not taken globally. In much the same way I cannot survey people from Manhattan, from all different backgrounds, and measure happiness for all humans. Different environment entails different parametres. Happiness remains very subjective and is based on many different things. If we knew what constitutes it we would't be having this discussion.

I agree, there are many flaws in the study I just found it interesting, like I said it was done as an economics study and they are just trying to make a generalized model that they can make assumptions from. Maybe I should put a clearer disclaimer in that paragraph though.

So why do people continuously work even after they become extremely wealthy?

I agree, like I said at the end it becomes a high score to them.

After a while you would realise that giving back to the community gives you more happiness. You will start investing and thus making more money.

I would probably do this along side my job and if I was extremely wealthy I would do it as a full time thing. I agree that would probably bring more happiness to my life.