This link: https://insights.rkconnect.com/5-roles-of-the-headline-and-w... says "Only 22% only read the headline of an online news story, according to data from the Rueters Institue for the Study of Journalism."
But following the link to that study gets me to https://reutersinstitute.politics.ox.ac.uk/sites/default/fil... which… if it supports that claim, I can't seem to find where :P