And what on Earth could I possibly mean by that? Here we go. If you spend any time at all driving in the rain in California (and you won't, because it never, ever rains here), you'll immediately notice that traffic is always absolutely fucked (even more so than usual) every time a single drop of rain threatens to think about forming somewhere in the upper atmosphere. Why is this? It's not because everyone drives like an idiot, which is the conclusion everyone jumps to. No, that's the reason that traffic is usually fucked it's normal amount. The reason for the additional fuckage is because different people respond in different ways. When the roads are dry, the distribution of velocities of the cars out there probably looks pretty much like a bell curve, centered around say 70 MPH. Things are bad, but generally speaking most people are trying to do the same thing at sort of the same speed, and some flow of cars in and out of the system does actually manage to happen. But what happens when it rains? Some people carry on as if nothing had happened, and some people slow down drastically, say to 50 MPH or something. Sure, some people slow down a medium amount, but generally speaking what happens is that you create a bimodal distribution, with a big chunk of the population going one speed and another large chunk going another. Obviously this is just bad news for everyone, because now you have way more cars going past each other and changing lanes on top of the reduced visibility and stopping distances and boom way more accidents and way more traffic.
Costco at lunchtime is exactly like this. One segment of the population is making a day of it; the members of this segment amble about nearly aimlessly, on the lookout for the next 14 gallon jar of mayonnaise they didn't know they couldn't live without until this very moment. Then there is the other segment of the population. I am a member of that segment, and we shop with a certain degree of...how can I say this...urgency. We are not looking to add things to our cart, oh no, we are simply trying to get all the items on the list that our spouses emailed to us and get the fuck out of there in time to not miss a meeting at 1pm. And obviously when you mix two populations you basically get the 5 north.