Number of nations in which average happiness was assessed in general population samples
| 1946 - 1955 | 8 |
| 1956 - 1965 | 20 |
| 1966 - 1975 | 30 |
| 1986 - 1955 | 48 |
| 1996 - 2000 | 65 |
| 1990 - 2000 | 90 |
| 1995 - 2005 | 95 |
| 2006 - | 135 |
An overview of nations and questions used per era is on the case list
States of Nations is an inventory of country characteristics. It is part of the World Database of Happiness.