If your average attendance is 5500, then +/- 1500 is a huge margin of error - roughly 27%.
On the positive side, it can me a lot more income when that 25% - we'll round down to make conversation easier, show up and pay their membership fees often at that high at the door rate. But it also means that you must build in a minimum of a 25% extra capacity in your program book orders, at con supplies, and other items that are given to each member. That's great, but only IF the float goes up.
If you float goes down, it's not necessarily a financial train wreck, most conventions have an excellent idea of the memberships they have already sold. You have the expense for the overage, but now you also have to cover the cost of their not attending. On the membership side, they paid in advance so no loss there. But it can impact costs that are contingent upon room reservation rates, like ballroom and meeting room space. You also now have all that extra "stuff" - con books, programs, gift bags that you need to store, sell, or worse just throw away. The bigger financial hit comes from a different direction, the lower number of potential sales in dealers room, art show, and explaining to your potential future advertisers / display groups why you were so far off your ATTENDING membership estimate. Fewer people in attendance means less money available for the dealers and artist. As I was pointed told by a former local convention advertiser, ".. it does me (the movie company) no good to send you (the convention) movie posters / displays / promotional material when few people are there to see it or pick them up." A 5,500 official attendance is far less impressive when only 4000 people actually are there to see the show.
Statistically speaking
On the positive side, it can me a lot more income when that 25% - we'll round down to make conversation easier, show up and pay their membership fees often at that high at the door rate. But it also means that you must build in a minimum of a 25% extra capacity in your program book orders, at con supplies, and other items that are given to each member. That's great, but only IF the float goes up.
If you float goes down, it's not necessarily a financial train wreck, most conventions have an excellent idea of the memberships they have already sold. You have the expense for the overage, but now you also have to cover the cost of their not attending. On the membership side, they paid in advance so no loss there. But it can impact costs that are contingent upon room reservation rates, like ballroom and meeting room space. You also now have all that extra "stuff" - con books, programs, gift bags that you need to store, sell, or worse just throw away. The bigger financial hit comes from a different direction, the lower number of potential sales in dealers room, art show, and explaining to your potential future advertisers / display groups why you were so far off your ATTENDING membership estimate. Fewer people in attendance means less money available for the dealers and artist. As I was pointed told by a former local convention advertiser, ".. it does me (the movie company) no good to send you (the convention) movie posters / displays / promotional material when few people are there to see it or pick them up." A 5,500 official attendance is far less impressive when only 4000 people actually are there to see the show.