Part of the October boost is probably caused by a significant increase in road toll for any ICE-powered car entering Oslo, introduced (if memory serves) October

Part of the October boost is probably caused by a significant increase in road toll for any ICE-powered car entering Oslo, introduced (if memory serves) October 1st. Roughly half the population of Norway live within an hour's drive from Oslo (this is probably a slight exaggeration, but emphasis on 'slight') - so this increase probably served to boost sales of any toll-exempt vehicle instantly.