Archibald
Banned
OK.
Anyway, if we get 10-18 million less deaths due to no WWI and 75 million less deaths due to no World War II, and if we add another 20 million people who wouldn't have died had the Spanish flu been less severe (due to less troop movements and travelling during this time), and if we factor in population momentum to these calculations (due to the young age structure of this population as well as the fact that many of these people would have probably had a lot of children had they lived), we'd probably see 300-400 million additional people in Europe + North America + East Asia.
Of course, these figures would probably be even better if the rise of Communism is butterflied away.
Also, with no Communism, both Eastern Europe and East Asia would be much wealthier on a per capita basis right now. Else, though, there would probably be little to no effect on per capita wealth.
Plus all the ten millions of people killed by Mao and Stalin outside WWII. Things like Holodomor (you know, the Ukraine famine of 1932) and Great leap forward.