For context: This graph has been used by activist in the queer community as to why there are “more queer people nowadays”. It’s not that there are more queer people, it’s that more people nowadays identify as queer due to there being of a stigmatization of being queer. This graph shows that if something is less stigmatized more people will be honest about it. This is because in the early 1900’s writing with your left hand was seen as demonic and unnatural (ironic, right?)
my guess is across ww2 and korea, left-handed soldiers were killed more because the equipment was made for right-handed individuals primarily, and there is a suspected genetic component to dominant-handedness. less lefties making kids means less lefties overall, but it obviously recovers to a steady rate