Since Cadet Stimpy provided me with a way to get all BGG data in a simple spreadsheet, I have been able to produce a few plots that may be of interest to you!
- First of all, the data has been extracted in 2020. This means that the data for the 2020 year is not complete. Although there were already games in the database at that time with a year published posterior to 2020, they were few. So, I have set aside 2020, 2021, and 2022 for the "number of solo games released" plot. I also filtered out the entries by only keeping the games that are actually owned by at least 50 people.
- But this doesn't tell us much -except 'it's a lot!'. What's more instructive is how many games published are soloable - so we have an idea of the evolution of the "share" of solo games among all the releases. Here I kept the 2021 data (because it's a ratio), but not the 2022 (because all the games are soloable: it's only a bunch of Kingdom Death Monster expansions that people marked as "owned" because they have pre-ordered them). So here is the plot:
I think the last two data points are not too reliable, but even from 2019 we have a ratio of 40% which is huge.