Newspaper Dagens Samhälle mapped the changes in income in Sweden's municipalities over a five-year period and found that the number of households classed as rich grew in 273 municipalities, while the number defined as poor grew in 264. The sharpest changes occurred between 2014 and 2015.
The study defines poor households as those which earn below 60 percent of the median income, and rich as those which earn more than 200 percent of the median. The most extreme example of concentrated wealth is Danderyd municipality in Stockholm, where 36.6 percent of households fall into the rich bracket as of 2015.
Jesper Roine, an associate professor at the Stockholm School of Economics who specializes in researching wealth inequality, explained that the growing gap is being driven by earnings from capital, rather than a change in wages.
"The explanation is the importance of capital income – which is mostly concentrated at the top end of wealth distribution – has increased. At the same time, the social security system has not followed general wage developments, which means that those at the lower part of wealth distribution lag behind," he told The Local.
"But in terms of wage distribution – which is closely tied to the still relatively centralized collective wage negotiation model – things have hardly changed at all in recent decades," he added.
Capital income made from the sale of housing and shares accounted for 15 percent of total disposable income among Swedish households in 2015. Almost 90 percent of capital income made in the country during that period went to the 10 percent of the population with the highest income.
Dagens Samhälle's survey also served as a reminder that Sweden is not immune to the urban-rural divides which have helped shape votes in both the US and UK in recent years.
The study showed that 14 of the 20 municipalities in Sweden with the greatest proportion of high income earners are in the Stockholm county. Only two of those 20 municipalities are in an area not classed as part of a large city, meanwhile.
Despite the new research, Roine thinks Sweden is still a relatively equal society on an international level – just not as exceptionally equal as before.
"Sweden is still a very equal society compared to most other countries. But it's true that gaps in income have grown, and Sweden is no longer as different as it once was in that sense," he concluded.