I'm going to guess here and the poster can fill in details - I guess that they live in a rental owned by the municipality.

The rents for these are not market-based but instead based on a fairly complex system of pricing based on the standard of the apartment, with rent increases being negotiated by the renters union.

This system has some merits - it has definitely kept rents pretty low for rentals in Sweden generally - but has also been a part of shaping the very dysfunctional housing market we see in Sweden today.

Basically, Sweden had low standards of housing in the mid-1900s, at which point the left-wing governments started a program called Miljonprogrammet, basically a housing program to build a million homes, which should be affordable and of high standard. This program started in 1965, hence my suspicion that the OP lives in this type of apartment.

The program is considered a bit controversial today as the areas built under this program are now basically the high-crime areas in Sweden in many cases. This is not inherent to the program though, but instead a consequence of the fact that this program was so damn successful at fulfilling its job that Sweden had an affordable housing surplus for decades after that program was started. Affordable housing construction basically stopped once the program was over and only co-ops and houses were built after (an overstatement but broadly true). Later, right-wing governments ran programs to sell off this housing stock to private interests which managed them in a slumlord fashion, leading to their current reputation.

Anyway, the current situation of housing in Sweden is that the housing market is bifurcated - you can apply for municipal rentals, which have waiting times upwards of 20 years in attractive cities, or you can get a massive loan and buy either a co-op apartment or a house. There's generally a shortage due to the lack of building for so many years. If you manage to get a municipal rental, you can expect to pay a rent that is far lower than servicing a loan in a similar area, but the standard of the apartment will usually be lower.

For what it's worth, I think that reintroducing a program such as Miljonprogrammet again is the only true way to curb the housing market situation in basically every rich country with a housing crisis. The whole concept of gentrification only exists in the context of housing scarcity. It's pitting workers against workers in a really nasty fashion. A better way forward is to build housing like there's no tomorrow. Government-owned, high standard, low-cost housing.