I am going to make a wild claim: "Happiness" is a stupid metric for quality of life. So many of the answers are tainted by local culture. Most Japanese people would feel like they are bragging to say they are somewhat or very happy. The very question is flawed. And I guarantee the survey was created by people with mostly Western European culture. To be clear: I said "quality of life" not happiness. There is a big difference. Let me tell you what "works" in Japan: health care, education (primary, secondary, and tertiary), home buying/building (wildly cheap by world standards), labor protections, national pension, mass transit, personal safety, taxation... I could go on and on. Quality of life is objectively extremely highly in Japan when compared to other nations.