My fundamental belief: Money doesn't bring happiness, but the lack of it brings unhappiness.

The author of https://ofdollarsanddata.com/ has a new book that has a couple of chapters that go into this:

* https://ofdollarsanddata.com/the-wealth-ladder/

The research he cites finds that happiness starts levelling out at Levels 3-4 of his framework. Some of his posts on the subject:

* https://ofdollarsanddata.com/?s=happiness