What percent of wars are caused by religion?

looking throw history i think it would be safe 2 say well over 50% i have heard up 2 90% and as low as 17%....17% is way 2 low and 90% might be a little high. anybody know? preferably a Atheist answer this Q so 2 have no bi-est Christians?
Update: like for example. the crusades. japan attacking us in world war 2(believed they were lead by a god and couldn't lose) Muslims attacking the Jews.
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