In all, 18 rape judgments were handed down from 2009 to 2011 in the south-western city, according to a review carried out by state broadcaster NRK.
The cases involved 22 men, two of whom were cleared of rape charges.
Of the 20 men found guilty of rape, half were of African origin, five had Asian backgrounds, one had Polish roots and three were ethnic Norwegians, said NRK, which did not disclose the ethnicity of one of the men.
Police investigator Kristian Johansen said he was surprised by the figures, as men with immigrant backgrounds were not overrepresented to the same extent in cases reported to the police.
“When we look at the total number of reports we process, the cases involve a higher number of ethnic Norwegians. It surprises me that so few ethnic Norwegians have been convicted,” he said.
By contrast, Stavanger district court judge Helge Bjørnestad said he was not surprised by the figures.
“I don’t think this is an arbitrary grouping. Unfortunately, it tallies with what we’ve seen,” he said.
Bjørnestad added that it was important for the figures to be out in the open if there was to be a meaningful discussion on how best to prevent further rapes. .
“A perpetrator analysis can be absolutely decisive in many contexts. By pointing this out and discussing it, it becomes possible to use effective remedies. When choosing the remedy, you need to know who the perpetrator is,” said Bjørnestad.
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Commenting on the skewed ethnic distribution of culprits, the judge said this could be partially explained by cultural differences.
“There’s clearly an explanation that’s tied to views about women, respect, and integrity. But that’s hardly the entire explanation,” he said.
Norway has recently been seeking to fight back a rising tide of rapes, with the number of reported rapes by strangers spiralling to record levels last year.