The theoretical construct for measuring and understanding happiness has different meanings in psychology. In this study we mainly analyse objective factors of happiness, such as economic, social and environmental well-being, factors that can be driven by social science and policy measures.  

Until now, the data offered in support of these conclusions were mostly based on point, cross-sectional data. Easterlin and O'Connor's longitudinal study has an interesting battery of data that provides a time span of 36 to 37 years, collected from 1981 to 2018 in 10 European countries.  

One of the limitations of the data is on air pollution, because they became available only in 1990 and do not correspond directly to the full period. However, they complemented the time series analysis with a fixed effects analysis that exploits the multiple corresponding periods. 

Among the most widely accepted theories of happiness in the scientific community, happiness is defined as a part of subjective well-being. It is defined as the way people experience the quality of their life in three different but interrelated mental aspects; infrequent negative affect, frequent positive affect and evaluations of life satisfaction.  

The cognitive and behavioural strategies that people choose in their lives strengthen or weaken the components of subjective well-being and happiness, rather than environmental conditions and/or economic growth. Well-being can also be measured objectively through the quality of life provided by the availability of goods and services, economic growth, social capital, welfare state and environmental policies, variables measured in Easterlin and O'Connor's article. 

It is a valuable study because, in addition to promoting measures to improve the objective component of well-being, it provides longitudinal and cross-sectional data. This allows us to see how the relationship of the variables measured changes depending on whether the data are collected over short or long periods of time. In addition, the authors argue that in the long term, the purely objective variables of well-being, economic and social status, become less related to happiness.   

The study fits with the existing evidence, income and happiness paradox in the long run, also by author Easterlin, and presents new evidence available from important time series that supports the importance of welfare state policies. In the collected long-term time series data, economic variables, social capital and environmental quality have no relationship with happiness, contrary to what was found in cross-sectional studies and in the present study when analysing recent data cross-sectionally.  

Cross-sectional data may give a misleading impression that economic growth, social capital and/or environmental quality drive happiness trends, as it has been found in long-term time series data that these variables have no relationship with happiness. It is likely that the cross-sectional regression result pointing to GDP as the main driver of happiness, and possibly the other significant cross-sectional variables, is a statistical artefact. 

Limitations of the study include that the results are based on a limited set of European countries, although the main limitation may lie in the focus on objective well-being variables. As a future proposal, a greater boost to subjective well-being from social policies, rather than a purely economic and environmental improvement, is needed. The latest studies on happiness give more weight to working on the three-dimensional axis of subjective well-being, negative affect, positive affect and assessment of quality of life, than to economic income. To improve the level of happiness of their citizens, European countries could also invest in mental training programmes to optimise the aspects closely linked to human happiness.  

The main finding of this time-series study of 10 countries in Northern, Western and Southern Europe was that happiness increases with generosity and happiness decreases with a decrease in the generosity of welfare state programmes. The implications of how a country can increase happiness in real life cannot remain only in the objective aspects of happiness, but extend to the subjective ones. In longitudinally collected data, changes in generosity are more predictive of changes in happiness than economic conditions, social capital and environmental quality. Generous welfare programmes are the apparent key to happiness, and this is where future longitudinal studies and investment by countries to increase the happiness of their citizens should go.