I’m not sure if there are publicly available stats but my first guess is that there are more users migrating from Reddit, probably because they’re not happy with the demographic shift.
I haven't followed this -- what's the demographic shift of Reddit about?
Aside of that, I think somebody on HN also pointed out that it is now easier to get downvotes here, because of an emerging trend to use downvote as an indicator of disagreeing with the OP or GP. Maybe the rise in upvotes is also part of the same "paradigm shift" (which I personally wouldn't like).
It would actually be great to have a HN user-level option that hides all vote/point counts, including the ones given to your own posts. Can probably be easily done with some browser addon, though, but a HN option would be nicer.