It's possible if the government plays around with the tax system too much while being composed of idiots who don't understand basic math or don't understand why tax rates over 100% are bad.
As an example, former Croatian prime minister Jadranka Kosor introduced a new tax according to which if your after-tax income was above a certain limit, you had to pay an additional 4% of that income as tax. Of course this resulted in >100% marginal tax rates.
I assume Sweden had a similar situation, where it wasn't actually a 102% tax rate, but a combination of multiple different taxes that resulted in an effective tax rate over 100%. The people who created those taxes either didn't care or were simply too stupid to notice the problem.
It wasn't that common, but it was a real phenomenon that personal income marginal taxes could exceed 100 %. The Social Democrats in Sweden got angry when Astrid Lindgren pointed it out, and it seems some Hacker News readers with a downvote button become angry in the same way when this is mentioned.
