> Probably! But I don't know what it is, or what its conclusion is, so just saying that it probably exists doesn't advance either of our arguments.

https://www.nature.com/articles/s41380-018-0263-6

30-60% according to a bunch of studies. This particular study puts it closer to 60% than to 30%, which is in line with my own expectations but it's not a settled research question yet.