Is this good data?

Norway...
exported 15 000 tons of aluminum annually to the german war industry.
The export of herring (a fish) rose from 10 000 tons in 1939 to 54 000 tons in 1944.
We exported 30 000 tons of codfish annually.
More than half the amount of the fish consumed by the germans came from Norway.
(Source Aschehoug: " History of Norway", volume 11, page 87.)

No, this was really not good. When WWII broke out in September 1939, Norway as a part of the Declaration of neutrallity stated that the trade with Germany should cary on at 1938 level. But - alas - as a part of beiing occupied, the occupants had the power to increase the trade. Just logic that Germany would increase the trade with Norway, regardin commodities that were scarse in Germany

I meant more was it accurate.

There's some interesting files in The National Archives - Kew, London - on the goods/material that was coming out of Norway. Of course, you have to treat the figures with an open mind, but if you can compare with similar figures from your source then you can draw conclusions. Unfortunately, I cannot recall the file number, but it's worth trawling the 'Catalogue' online at the TNA to get the file you want. The TNA, for a fee of course, will copy and post the copies to you.

Cheers

Bob