I was using Google Ngrams to investigate whether feminine pronouns have been used more often in English literature over time, relative to masculine pronouns. I was surprised to find that the percentage of all pronouns out of all words being written dropped steadily from 1800 to 1980 and then shot up between 1980 and 2020 in this graph.
What could explain why the prevalence of all pronouns would change in parallel with each other? Does it reflect real change in usage or is it an artifact of the Ngrams archives?