The mystery of em‑dashes: part two with quantitative evidence

A couple of weeks ago I made an assumption: the rise of em‑dashes in AI‑generated text happened because model providers started scanning older, pre‑Kindle books.

Google Ngrams shows that em‑dash usage peaks before large‑scale digitalisation, so if those books suddenly enter the training mix, the punctuation habits of the past hitch a ride into the prese…