At least 50% more war loot with each age. I'm global, and it costs me 3200 oil (1200 for generals and 2000 for planes) per war attack. That's 6400 oil for both war attacks. IF we win the war, I get that back, but only just. Global base war loot should be 4000, Atomic 6000.
I am considering not warring because of this, or changing my approach. My current alliance is great, but we try to win until all hope is lost. We need to swallow our pride, size up the opposition realistically, and not even try if the chance of winning is less than 40%. Just go for the easiest base of the same age that I can get at least one star against without using any oil, and not too much food.