I saw an article by UNICEF about the context of their work with some eye-opening statistics. If they're referenced, I couldn't see the reference:
Civilian fatalities in wartime climbed from 5 per cent at the turn of the century, to 15 per cent during World War I, to 65 per cent by the end of World War II, to more than 90 per cent in the wars of the 1990s.
The context is talking about civilians (and particularly children) being increasingly affected by wars as the nature of war changes, so it's fair to assume it means the percentage of fatalities (presumably, all deaths, therefore including disease famine etc) in wartime who are civilians.
Is this true?
We've got a related question on a similar topic but there are a number of differences: casualties of war are different to fatalities in wartime, this claim is the 1990s while that covers wars in the 2000s, the claimed figures are different, etc etc.