  Based on one million arXiv papers submitted from May 2018 to January 2024, we
assess the textual density of ChatGPT's writing style in their abstracts by
means of a statistical analysis of word frequency changes. Our model is
calibrated and validated on a mixture of real abstracts and ChatGPT-modified
abstracts (simulated data) after a careful noise analysis. We find that ChatGPT
is having an increasing impact on arXiv abstracts, especially in the field of
computer science, where the fraction of ChatGPT-revised abstracts is estimated
to be approximately 35%, if we take the output of one of the simplest prompts,
"revise the following sentences", as a baseline. We conclude with an analysis
of both positive and negative aspects of the penetration of ChatGPT into
academics' writing style.
