If you read that paper carefully (it's been a while so I might have this wrong), I think you'll see that while they're using Norman vs not-Norman surnames, the

If you read that paper carefully (it's been a while so I might have this wrong), I think you'll see that while they're using Norman vs not-Norman surnames, the comparison is between Victorian and contemporary wealth and life expectancy data. (Obviously the discrepancy has to start with the Conquest, I'm just saying that strictly speaking you can't use that paper to support that conclusion).