We received our 14,000th submission at Strange Horizons yesterday. At the current rate of submissions, I'm expecting we'll reach 15,000 sometime in October.
In case you're curious, around 6100 authors have submitted to us over the six years since we received our first submission. (This coming Tuesday, 27 June, will be the sixth anniversary of the day we received our first submission.)
In other news, the switch to the RTF submission form has been a success; out of the 79 stories submitted in the first seven days after we switched, only 5 didn't use the RTF form. I'm kind of surprised by that, actually; it suggests that information spreads very quickly through the writer community (or else that almost all writers actually do check guidelines before submitting, but that seems unlikely). But I guess I've seen something similar before, when we announce our annual December closure-to-subs and submissions instantly dry up.
I was a little worried that submission volume would go up significantly with the advent of the RTF system, but so far it hasn't; it was already higher than usual for the two weeks before the RTF changeover, and this past week it's stayed at about the same level as those previous two weeks.