On the happiness roller-coaster with SDR 2.0 data
This paper introduces the Survey Data Recycling 2.0 (SDR 2.0) database as a comprehensive resource for subjective well-being research, detailing its harmonized individual-level data across 156 countries and demonstrating its potential to advance cross-national and longitudinal studies on topics such as the Easterlin paradox and the determinants of life satisfaction.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
For decades, scientists have tried to map the landscape of human happiness. They ask people to rate their lives on a scale, from feeling terrible to feeling wonderful, and then look for patterns. They want to know if money makes us happier, if trusting our neighbors helps, or if the happiness of a nation grows as its economy grows. The challenge has always been data. Most studies rely on a handful of large surveys that ask similar questions, but these surveys often stop at national borders or end in the 1990s. To understand how happiness changes over a lifetime or across the entire world, researchers need a much bigger, more continuous picture, one that stitches together thousands of different surveys from nearly every corner of the globe.
A new study by Francesco Sarracino and Giulia Slater offers exactly that picture. They have built a massive digital archive called SDR 2.0, which combines information from 23 different international survey projects. This archive covers 156 countries and more than 4.4 million people, stretching back to 1966. The researchers did not just dump these numbers into a single pile; they spent years carefully translating different question formats and scales so that a "7" on a happiness scale in one country means the same thing as a "7" in another. By doing this, they created a tool that allows scientists to ask questions about human well-being that were previously impossible to answer, revealing how happiness rises and falls across time and space.
The first thing the researchers checked was whether the way a survey was conducted actually changed the answers people gave. They looked at technical details, such as whether a question was asked on a scale of ten points or eleven, or whether the survey asked about money before asking about happiness. They found that while some of these details did nudge the scores slightly—for instance, people tended to report slightly higher satisfaction when asked on an eleven-point scale rather than a ten-point one—these technical quirks did not distort the big picture. The overall trends in happiness remained clear and stable, regardless of the specific survey program or the minor variations in how questions were asked. This gave the researchers confidence that the data was reliable enough to tackle the biggest questions in the field.
One of the most difficult puzzles in happiness research is the role of money. In the database, the researchers could not simply add up everyone's income because different surveys asked for it in different ways, using different currencies and different definitions of a household. Instead, they created a new way to measure wealth based on where a person stood in their own country's income ladder. A person in the bottom 20 percent of earners in a rich country might have more actual money than someone in the top 20 percent of a poorer country, but the database treats them as being in the same relative position. To fix this, the researchers developed a method to estimate actual household income by combining this relative position with data on how national wealth is distributed. They tested this method against high-quality original data and found it worked well, capturing the general shape of income distribution even if it smoothed out the very highest and lowest extremes.
With this improved data, the researchers revisited a famous idea known as the Easterlin paradox. This idea suggests that while richer countries are generally happier than poorer ones, a country's happiness does not necessarily increase as its economy grows over time. The new data allowed the team to look at this relationship over nearly forty years. They found that the paradox is not universal. In North America, Europe, and Oceania, economic growth has not led to a corresponding rise in life satisfaction; the lines on the graph have stayed flat or even dipped. However, in other parts of the world, such as Asia and Africa, economic growth has been accompanied by a steady increase in happiness. This suggests that the link between money and happiness depends heavily on where you live and how long you have been developing.
The study also explored how social trust changes the way money affects happiness. The researchers found that people who trust others generally report higher life satisfaction. More importantly, they discovered that trust acts as a buffer. In societies where people trust each other more, the gap in happiness between the rich and the poor is much smaller. When trust is low, being poor feels much worse, and being rich feels much better, creating a wide divide in well-being. But in high-trust societies, that divide shrinks, suggesting that social connections can soften the blow of economic inequality.
Finally, the team looked at whether countries are becoming more similar in their happiness levels over time, a process called convergence. They found that countries starting with lower levels of happiness are indeed catching up, growing faster than those that started with high levels. However, the overall spread of happiness across the world has not narrowed. Instead, the differences between countries have actually widened and then stabilized at a higher level of inequality. This means that while some nations are improving, the world as a whole is not becoming more equal in terms of well-being. The researchers conclude that this massive new database is a powerful tool for understanding the complex forces that shape human life, offering a clearer view of how we live, what we value, and how our circumstances change over the long arc of history.
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