This is the article from a week ago that talked about the data up till that time.
As of Tuesday, Iceland had tested more than 17,900 people for the virus -- nearly 5% of its population. And while its National University Hospital tests people who are high-risk or show symptoms, nearly half of Iceland's tests have been conducted by biopharma company deCODE Genetics, focusing on the the wider population.
Some of the revelations have been stark. Although fewer than 1% of the (deCODE) tests came back positive for the virus, the company's founder Dr. Kári Stefánsson told CNN that around 50% of those who tested positive said they were asymptomatic, confirming multiple studies that show that asymptomatic, or mildly symptomatic, people have played an important role in spreading the virus.
https://www.cnn.com/2020/04/01/europe/iceland-testing-coronavirus-intl/index.html