On the other hand, this German study, which is based on leukemia patients, found a non-paternity rate of 1%. Leukemia patients are handy because they're randomly distributed throughout the population. It's possible that Germans are very different than North Americans, but it's also possible that the non-paternity rate is WAY lower than some "estimates."

from the abstract

...the nonpaternity rate in the population of 0.94% was obtained with asymptotic 95% confidence limits of 0.33% and 1.55%, respectively. This result is in accordance with recent surveys as well as findings from Switzerland for a comparable sample, and it suggests that earlier estimates of the nonpaternity rate which were often in excess of 10% may have been largely exaggerated.

It's unlikely there is much, if any difference at all, between culture's paternity fraud rates (this is a biological thing). Since you're already seething with condescension, It's also possible the norwegian social sciences are highly corrupt, (evidenced by several scandals and falsifications of research, but there's also a fun documentary on it Brainwash), and any study agreeing with them should be examined critically, becuase there's a good chance they're part of the same 'no biological explanation for anything' fringe subgroup of psychologists.