HELSINKI — Finland has topped an index of the happiest nations for the second consecutive year, with researchers saying the small Nordic country of 5.5 million has succeeded in generating a happiness recipe for a balanced life not simply dependent on economic and material wealth.

The World Happiness Report, produced by the UNSustainable Development Solutions Network, ranks 156 countries by how happy their citizens see themselves to be.

It’s based on factors including economic wealth, life expectancy, social support, freedom to make life choices, and levels of government corruption.

The index, published Wednesday, showed the other Nordic countries did well again this year, with Denmark, Norway, and Iceland taking the next spots. The remaining top 10 nations were The Netherlands, Switzerland, Sweden, New Zealand, Canada, and Austria.

The United States dropped from 18th to 19th place despite enjoying a booming economy in the past few years.

The report noted that, in general, happiness levels have decreased worldwide despite continued economic growth. That’s partly explained by ‘‘dramatic falls’’ in happiness in population-dense countries including the United States, Egypt, and India, it said.

‘‘By most accounts, Americans should be happier now than ever,’’ wrote professor Jean M. Twenge from San Diego State University, referring to low unemployment and crime rates, improved living standards. and income levels.

She suggested that a factor could be the substantially increased time Americans are spending on electronic devices and social media, habits that have led to low in-person social interaction and decreased sleeping time.

associated press