"based on an analysis of more than 17,000 songs from the US Billboard Hot 100."
Having lived and listened through the entire period I recall several "upheavals". "Dead Skunks in the Middle of the Road", "My Ding-a-Ling", "Grandma Got Run Over by a Reindeer" ... Bit like determining the eating trends of a city by looking at the fast food wrappers in a landfill.