Tuesday (March 20) is International Day of Happiness and, as they’ve done every year, the United Nations has published the World Happiness Report. The U.S. ranks 18th among the world’s countries, with an average life satisfaction of around 6.88 on a scale of 10.

While that may be relatively near the top, America’s happiness figures have actually declined every year since the reports began in 2012, and this year’s are the lowest yet. The question, then, is whether the government has a role to play in improving the happiness of its citizens. And if so, how might policymakers go about it?

Fortunately, a growing body of work by economists and psychologists can give governments access to the kind of data that can inform the way they think about policy and happiness.

In our new book, “The Origins of Happiness: The Science of Well-Being Over the Life Course,” my colleagues and I provide a systematic account of what makes for a satisfying life.

The Role Of Government

The idea that government ought to focus attention on the well-being of its citizens goes back centuries. Thomas Jefferson himself said, “The care of human life and happiness … is the only legitimate object of good government.”

Historically, this has meant increasing economic productivity and growth to increase personal happiness. But as the data suggest, and many countries are beginning to realize, this isn’t likely to be sufficient. As a result, many governments around the world are now taking steps to broaden their policy goals beyond GDP.

This is not just a question of leaders being benevolent. Electoral data suggests that governments of populations that are unhappy do not tend to stay in power very long.

But how can governments change the way their citizens feel? Ultimately, changes cannot be made without good data. If governments are going to use well-being as a serious measure of success and progress, they need solid evidence of what lies behind people’s happiness and misery.

To make rational decisions about where to spend finite public funds, they need to know how potential policy changes will affect people’s well-being -- and at what cost. Without these numbers, governments risk looking for happiness in all the wrong places.

Causes Of Happiness And Misery

For “The Origins of Happiness,” my colleagues and I analyzed a large amount of survey data from around the developed world in order to document what determines life satisfaction over the life course.

We found that income plays an important role in determining happiness -- but it’s not as significant as people might think or expect. Highly important are social relationships, be they at home, in the workplace or in the community.

That suggests that, to boost happiness in America, policymakers should look to counter adverse trends in inequality, the erosion of social trust and increasing isolation.

Our research finds that mental illness explains more of the variation in happiness than physical illness. In the U.S., mental health problems, including depression and anxiety, are a major cause of suffering. Yet many can be treated, for example through evidence-based psychological therapy. Public health spending on mental illness is therefore not a luxury, but a necessity.

In fact, our calculations in the book suggest that mental health treatment usually turns out to be cost-neutral, given the large benefits that alleviating mental health problems brings in terms of lower physical health care costs, absenteeism and crime, as well as increased productivity.

Much of increasing happiness in adults begins with addressing the needs of children. We found that schools -- and even individual teachers -- have just as large an effect on the happiness of children as do their families. So schools and governments can and should do a great deal more to ensure that they teach the kind of key life skills and resilience that foster happiness, both in childhood and right through into adulthood.

Not surprisingly, the world of work has a huge influence on our happiness as adults, providing not only income but also important social interactions as well as routine and purpose. The leading drivers of a satisfying work life include job autonomy, work-life balance and the quality of social interactions with coworkers and managers.

Ultimately, a great deal more can be done to make work more satisfying and enjoyable. Again, the evidence suggests this is not a luxury, but can make for a more profitable business environment.

Policymakers now need a host of carefully controlled experimental trials of particular policies in order to obtain precise estimates of their effects on happiness — which can then be compared with their financial costs. And although a great deal remains to be done, the Enlightenment ideal of focusing government attention onto making life satisfying and enjoyable is slowly becoming an ever more viable reality.

George Ward is a PhD student at the Massachusetts Institute of Technology.

This article was originally published on The Conversation.