I wear shorts about 10 months per year, and I live near Washington DC. Judging from the number of funny looks I get, and the number of times perfect strangers stare at me and ask “Aren’t you cold?,” my behavior is puzzling at best.

The silly explanation is that I’m from California. But that should make me more sensitive to cold, not less! The real answer, naturally, is that wearing shorts in the winter is good economics.

The simplest economic comeback to the unwanted queries would be “Of course I’m not cold. I do own long pants. By revealed preference, if I were cold I wouldn’t be wearing shorts.”

But that’s not quite right. The truth is, I sometimes am uncomfortably cold as a result of my attire. So what gives?

The answer is that if I dressed more warmly, I would be more comfortable during the few minutes that I am outside (maybe 30 minutes per day), but less comfortable during the many hours that I am inside. It’s cold outside, but warm inside, so I maximize my expected utility over the course of the day.

Suppose that my optimal temperature is 70 degrees if I wear shorts, and 60 degrees if I wear long pants. It is 40 degrees outside, and 75 degrees inside. Suppose further that every 1 degree deviation from my optimum causes me 10 cents worth of suffering per hour.

Implication: If I wear shorts, my half hour outside costs me .5*(70-40)*\$.10=\$1.50, and my eight hours inside costs me 8*(75-70)*\$.10=\$4.00. Total discomfort cost of shorts: \$5.50.

In contrast: If I wear pants, my half hour outside costs me .5*(60-40)*\$.10=\$1.00, and my eight hours inside costs me 8*(75-60)*\$.10=\$12.00. Total discomfort cost of pants: \$13.00.

If this reasoning sounds familiar, you’ve been reading this blog quite a while. I have essentially just repeated my argument for having lots of kids.

Couldn’t I just bring a change of clothes with me wherever I go? Sure, but the inconvenience costs outweigh the benefits. Oh, and speaking of saving inconvenience costs, from now when people ask me if I’m cold, I think I’m just going to tell them I’ve already answered that question on my blog.