Even pro rata doesn't work. If you do it per 1000 people, 1000 people in Sweden would probably come into contact with fewer people than 1000 people in the UK. That's not to mention age demographics, race demographics (seemingly quite an important factor) etc. It's far too complex to make comparisons unfortunately.
Anyway, it looks like there will be a lot less social distancing over the coming weeks so we can see how that will work out for us.