Yeah, and Tekna a few years back was one of those pushing to get rid of the (now illegal) anti-competition contracts all employers made you sign. So while most people don't see them day-to-day (as in, they don't set tariffs and often don't negotiate your salary), they still influence a lot. And the salary statistics is very useful in leveling the playing field and getting what you're worth.

And the union deals on insurances, mortgage etc. saves me much more money each year than the union fee.

My estimate would be that at most 40-50% of developers are unionized in Norway (more for ops/IT-department workers). In Sweden that's more like 80%.

Even 40% makes a huge difference, though.