**4. Data used and sorted**

Using the datafile Trends In Nations version 2022, we restricted to time series that cover at least 20 years and involve at least 10 data points. This is to keep the eye on long-term change for the better or worse and reduce the influence of incidental outliers. This left us with 200 time series in 70 nations over ranges of 71 to 20 years in the period 1945–2021.

### **4.1 Sorting by decade**

The longer the time series, the fewer cases we have; only one nation in the longest series since 1945 (United States) and 44 nations for the shortest time series since 2000. To allow for analysis of change in happiness over longer and shorter periods, we sorted the findings by decade; since 1950s, since 1960s, …, until since 2000. With a few exceptions, these series go up to and including the year 2019.

### **4.2 Separate presentation of 2020–2021 COVID years**

For a limited number of nations, we also have findings on average happiness in the years 2020–2021 in which the COVID pandemic developed. As we will see in Section 5.4, this incidental disaster has lowered average happiness in all nations and with recovery data not yet available it would distort the view of the general trend. As 2020–2021 data are available only for a few nations, comparison across nations would also be marred if we took all the available years together.
