Well, we don't really separate walking and hiking in the Norwegian language (I actually had to google the difference).
According to Statistics Norway[1], 85% of the Norwegian population has taken a walk of 3 hours or less in the last 12 months (of 2014) and around half a walk of more than 3 hours.
I didn't find updated stats about frequency, but in 1998 46% of Norwegians went on walks for longer than 30 minutes at least 2 times a week [2]. I don't have a reason to believe it has changed significantly.
According to Statistics Norway[1], 85% of the Norwegian population has taken a walk of 3 hours or less in the last 12 months (of 2014) and around half a walk of more than 3 hours.
I didn't find updated stats about frequency, but in 1998 46% of Norwegians went on walks for longer than 30 minutes at least 2 times a week [2]. I don't have a reason to believe it has changed significantly.
[1] https://www.ssb.no/kultur-og-fritid/statistikker/fritid/hver...
[2]http://www.vg.no/forbruker/typisk-norsk-aa-gaa-paa-tur/a/303...