Americans showed “significant decreases” in happiness from 2005-2007 to 2013-2015, says the latest World Happiness Report.

The U.S. ranked as the 13th happiest country overall in the 2016 report, while Denmark claimed the top spot. Crisis-wracked Burundi took the bottom spot in the ranking of more than 150 nations.

The report involved Gallup polling and was put together by Sustainable Development Solutions Network, a group linked to the United Nations and led in part by economist Jeffrey D. Sachs, known for “The End of Poverty” and other books.

As part of the report, researchers looked at changes from 2005-2007, before the global recession hit, to 2013-2015, and found that 45 nations showed significant decreases in happiness, meaning a drop of 0.12 point to 1.29 points on a scale of 0 to 10.

The U.S. was among those decliners, with its slide of 0.261 point, while debt-laden Greece showed the largest drop, falling by 1.294 points. But the U.S. did manage to improve its overall ranking among countries to 13th, up from 15th a year ago.

“There is a very strong message for my country, the United States, which is very rich, has gotten a lot richer over the last 50 years, but has gotten no happier,” Sachs said, according to media reports.

“For a society that just chases money, we are chasing the wrong things. Our social fabric is deteriorating, social trust is deteriorating, faith in government is deteriorating,” he said.

After Denmark at No. 1, the top 5 is rounded out by Switzerland at No. 2, then Iceland, Norway and Finland. These relatively wealthy countries are “fairly homogeneous nations with strong social safety nets,” a New York Times report noted.

Go here for the full report.

The table below gives the 53 happiest nations, according to the 2016 report’s researchers.