Analyst Richard Florida has revisited previously-reported statistics and also researched social and financial information going back as much as 10 years. He says he's proved that the richer a country is, the more heavy music will be found there.

Florida - who admits he's not a fan of the genre, although he likes Black Sabbath - writes on Citylab: "What we found is that that the number of heavy metal bands in a given country is associated with its wealth and affluence.

"At the country level, the number of heavy metal bands per capita is positively associated with economic output per capita; with level of creativity and entrepreneurship; with share of adults that hold college degrees; as well as overall levels of human development, wellbeing, and satisfaction with life.