Mention Sweden to the average American and an idyllic image of a society with high levels of education, low levels of inequality, and homes decorated with stylish mid-century furniture is likely to come to mind. This isn’t entirely misleading. For much of the last century, Sweden wasn’t just prosperous; it was one of the most equal societies in the world — possibly ever.

Today one of the trends defining Swedish society is a rapid growth in inequality. In terms of ownership of both financial and real assets, the Scandinavian nation is now the sixth-most-unequal country in the world, ranking even higher than the United States. Sweden has more dollar billionaires per capita than the US, and these wealthy individuals control a larger share of national GDP than billionaires in other major economies.

What has kept the Swedish social contract from fraying entirely is that the country’s overall levels of inequality are relatively low. This is largely because income equality has, until recently, remained fairly stable among wage earners. But there are signs that this is changing and that inequality is now increasing among workers. How did this happen?