I used to fly a lot with SAS from the UK to Copenhagen,to Stockholm and on to Kiruna, to Oslo and on to Andoya. They certainly overbooked on a regular basis. It was staff from SAS, BA, Lufthanza, KLM and Aer Lingus who told me that 10 % was typical. The business travel agent who made all our bookings also confirmed it. That was a long time ago, before EC261, so, as I said in an earlier post, it is not surprising if the percentage is now lower.
SAS had another neat little trick. In winter it was quite common for the flight from Kiruna to Stockholm to be delayed due to bad weather so that you missed the last flight from Stockholm back to the UK. They would book you on the early morning flight and give you a voucher for a hotel room for the night. It's amazing how many times they would "forget" to initial the section on the voucher that said that SAS would pay. You get up very early the next morning to find that the hotel is demanding payment for the room and no SAS office is open to get them to authorise that SAS will pay it. You end up paying yourself and it was very difficult to claim it back. You soon learn to check the voucher carefully before you leave the airport, especially when you are a skint research student surviving on a grant and a pitiful per diem expenses allowance that wouldn't even cover the cost of a hotel room in Sweden.