> Without fail, for free events, there’s a predictable dropoff of around 30% of all RSVPs. If I have 50 people RSVP for an event, I’ll assume 30 or 35 will show up.<p>Be careful, though. An event I used to go to that was free decided to charge a donation of I think £5 to a charity because they were connected with the venue and having a fundraiser at the time. Instead of the usual approx 50% attendance, it went up to over 90% and there was a huge shortage of food, shortage of places to sit etc.<p>(It was a 2 day hackathon + conference event, including lunch, dinner, breakfast and lunch again. A comparable paid conference would have cost probably hundreds per attendee - £5 was nothing, but enough for people to see the tickets differently)