preface: the following comment is about environmental factors, not race!

Also, Norway has been a popular country for migrants for decades. If you come from a less developed country where, for instance, the quality of food and health care (factors relevant to IQ) aren't as good as in Norway then this surely influenced the IQ of your predecessors and hence you. If the share of such migrants is big enough to influence the average (I don't know!) then this could be an explanation.

https://www.ssb.no/en/befolkning/statistikker/innvutv/aar/_i...