Groups Are Sometimes Bell Curves

2025-08-05

I think that some groups have some bell shaped characteristics. Not all groups.

Like I think of income distribution isn’t that bell shaped: https://www.census.gov/library/visualizations/2015/demo/distribution-of-household-income–2014.html

But a lot of things are probably bell shaped, like male height in the US, rolling a pair of dice, temperatures.

Some things are bell shaped but where you are on the bell doesn’t really matter. Like obesity, I think Americans have gotten more obese over the past 70 years (I dont have the data but I am pretty sure it is true.) and so the body fat bell curve has shiften up over the years. But even if I would have been fat 70 years ago and on the slimmer side in today’s America, I still have to deal with the health issues that come with carrying a few extra pounds. Even if the obesity bell curve shifts around, biology is going to work the same way.

And so when making a mental model about certain things I think about bell shaped stuff a lot. Like we need to decide if we are going to send our kids to the public or private elementary school here. How are we going to judge the school, where on the bell curve does our public school lie, where does the private one? If we pay the extra money are we really gaining a lot? Does the bell curve line up with the school rating we can find online. If we send our kid to an average elementary school but ensure he has a lot of extra curricular support, would that be helpful for his middle school?

Also when I worked at my previous job (not my current one) I was at the higher end of the bell curve for salary. And so I was grateful, it is nice to be on the upper half of the US salary bell curve. If you zoom out for the bell curve for the world I am at the very very end. Similar I live in the bay area in California, definitely on the upper part of the bell curve for the cost of living, stuff, houses, and taxes costs more here. But also hopefully when we sell our house we will make money, in theory we could sell all of our stuff and move to Thailand and live really well.

But I also think about really weird populations, weird bell curves, like serial killers.

If I were to think about this, there are a bunch of serial killers and most of them are probably average at killing, hopefully most of them get caught. But there are probably some that are really skillful and perhaps they are so skillful or something that they aren’t caught. Also there are terrible serial killers, they are just super inept and dont have enough skill to murder anyone. They just plot and make feeble attempts.

This is how I think about the world sometimes, but dont get too caught up in bell curves, and they never apply to individuals.

-Gary