Given One Option, What Would You Choose?

There's a vending machine in the building where I work that lets you see inside. I find it fascinating because it fixes so many problems that traditional drink machines have: you can see exactly what you're getting, so there's not surprise Mountain Dew in place of your Diet Coke; there is an arm with a conveyor belt that lifts up to fetch the drink, lowers to the level of the dispenser slot, and slides it into the slot to minimize drop-induced fiz build-up; and if you don't get a drink it will try to dispense the drink again and if that doesn't work, it gives you your money back! I would so have loved designing and testing that. Why aren't there more of these babies?

Anyway, the top row is always all 20 oz Coke bottles. Yet, as refill day approaches, the distrubtion of drinks on the top row looks suspciously like an inverted bell curve. Something like this:

*
* * *
* * * *
* * * * * *
* * * * * * * *

The drinks on the right side had been there so long that every single one had red caps when all the rest had green (the sign of a contest change). When the machine got particularly low, someone was forced to buy one of them and it turned out to have reached its expiration date. It's interesting how people tend to choose the center first (I know I do - A5, all the way) and move outward, but they don't necessarily wait until a column is empty to do so. Statistics is everywhere. You cannot escape.