The yearly dots are the individual points of data; so the lines between e.g. 2021 and 2022, despite being the main visual marker, do not indicate a change that

The yearly dots are the individual points of data; so the lines between e.g. 2021 and 2022, despite being the main visual marker, do not indicate a change that happened in 2021 that leads to 2022, but rather a change that happened in 2022 compared to 2021. GPT 3.5 came out early in 2022, chatGPT later the same year. Lots of change and community discussion that year around this sort of thing.