Hi, Goldie. I haven't researched this, but my impression is that topics that appeal more widely to the general online audience (e.g. sports, politics) tend to attract more non-members than more specifically 'Medium' topics (culture, life, writing). In general, non-member reads do seem to be higher of late, but particularly for certain stories. As for earnings, 'member read ratio' seems to have an outsized effect on the amount paid per read, all else being equal.

That's been my experience, anyway. The patterns with which views climb then tail off also vary widely. Initial read ratio seems perhaps to influence this as well - a story that gets 70%+ in its first day after boosting seems more likely to get its spike early on in the 15-day window.