But we were briefly terrified. The 75% probability folks turned into acceptances a lot faster than the lower probability folks turned into rejections. Excel recalculated the expected number of guests as we updated our estimates with outcomes. I think it touched 170 briefly. And then came the late declines, and all worked perfectly.
Jeff Ely says that this is because people like us (or, more likely, like Susan).
An invitation is an option that can be exercised at any time before the date of the party. The people who did not respond immediately are waiting to decide whether to exercise the option. If she’s a true friend then this is because she has a potential conflict that would prevent her attending. She is waiting and hoping to avoid that conflict. When she is sure there is no conflict she will say yes.Our acceptances came early; the rejections, worryingly late. And so Ely's test suggests that folks liked us. Excellent.
The other people are hoping for an excuse not to come. Once they get a better offer, manage to schedule a conflicting business trip, or otherwise commit themselves, they will send their regrets.
In both cases, when the party is imminent, the option value of waiting is gone. Those who want to come but haven’t gotten out of their conflict give up and send their regrets. Those who hoped to get out of it but failed to come up with a believable excuse give up and accept.
So, a simple measure of how much your friends like you is the proportion of acceptances that arrive in the final days. Lots of acceptances means you better set aside a few extra drinks for yourself.