A lot of that is due to the fact that a large percentage of Norwegians are homeowners, and when a 1 bedroom apartment in Oslo can easily cost more than $200,000, well, that will add up quickly.
Their government has 350 billion / 4.7 million = 74,468$ in their oil fund per person including children. So the average person would need to be holding over 100,000$ in debt (including children) for that to balance out which seems fishy to me.