I'll add that this high rate is mirrored in several countries doing anti-body tests on blood donors (though one could argue blood donors are a self-selecting group):

>In this sample 11% has antibodies and the test detects 70-80% of people with antibodies. So, that leaves us with 14.6% immune. With a population of 2,377,081, that means 347053 people would be immune in Stockholm now, for an IFR of 0.27%.

[1] https://www.reddit.com/r/COVID19/comments/g4znbg/at_least_11...