Thanks, Luce. Yes, something weird does seem to happen with some stories getting a huge proportion of non-members views. Like they've been marked 'for export' by the algo.

My suspicion is that it happens more with pieces that have one or more 'mainstream' tags, like sport, politics, that general web users might be interested in. Rather than the more Medium-specific Memoir, This happened to me, Writing.

I haven't done any digging to see if that's borne out by my own stats, but there have been a couple of pieces recently that suggested such a hypothesis.