How much Scandinavian blood is in the veins of the modern day French Normans?

I asked this question before but didn't get the answers i need for it. I would like to know what percentage of Scandinavian blood is in the modern day Normans of France. I am French and of Norman heritage mostly so I am just kinda curious. When the Normans went on their raids elsewhere did they all leave or did some leave and some stay, or did many of them when first arriving in Normandy breed with the people with some of them staying while others left?