JUst returned home from a week in WDW. Never realized how much I hate fastpass. I would love to know the formula disney uses to determine the number given out. Also weather the number changes by the time of day.
The number does vary a bit, but the goal is to distribute for a maximum of 80% of a ride's hourly capacity, but also to allow room for rider switches, guest assistance cards, and other things, so the number of Fastpass tickets issued is closer to 2/3rd's the ride's hourly capacity.
This is why, on a really busy day, the return window being distributed can be several hours away.
In an ideal, perfect scenario, the number of guests using the Fastpass queue would be constant, never requiring the 4:1/80% ratio to be adjusted to 6:1 or higher. Meaning the maximum intake from the Fastpass queue would be 80% or less. (If there happens to be no one in the Fastpass queue, the standby queue intake jumps from 20% to 100% temporarily.)
However, that is not the case. People return in packs, not evenly, so the Fastpass queue demand fluctuates. The ride's capacity, while expected to be operating at 100%, may be decreased.
So, right there, are two flaws with the system - tickets are distributed under the assumption that people will return evenly spread out, and it distributes under the assumption that the ride will remain operating at 100% capacity.
Of course, when a ride *does* lose capacity, the number of Fastpass tickets that will be distributed is lowered to match the ride's decreased capacity. But it's too late, as all previous tickets were already distributed assuming 100% capacity.