Support Structures.

Most of what exists isn’t doing the thing. It’s setting the conditions for the thing to be done. Think about your body. You can move around this crazy world doing all sorts of stuff. Even compete in the Olympics, maybe. But to move, you need a skeleton, muscles, ligaments and joints and tendons. All that is in support of you moving. But those things need blood and vessels and the blood has to be pumped and oxygenated. Add more supports. You need digestion and that creates waste, along with cellular waste, more supporters are needed. All so you can bumble around in your bathrobe on a Sunday afternoon.

When you lose weight, you lose muscle too. And you lose some other bits, like blood vessels or total blood volume. These extra losses are because you have less tissue to support when you lose weight. The body doesn’t want to maintain extra muscle and blood vessels for tissues that don’t exist anymore. Or if you gain weight, it needs to build new support tissues It needs extra blood.

There are other supports, self-supports, like how much of the gasoline is used to transport the gasoline in your car, or how much of the battery’s energy is needed to move the battery if it’s an electric vehicle. That mostly gets boiled down to the notion of energy density, in practice.

And we can take that back to the body. Caloric density. How much energy a food gives you. In some cases it can be negative, when it costs the body more to digest than it gets back. But those foods can still be beneficial, if they provide fiber or some other nutrient or function. Weird.

Look at an organization. Most of the jobs aren’t there to do the thing. They’re there to help set the conditions, just like the body, just like the fuel system or battery system of a car is only helping, not the main task. You have human resources departments, you have sales or logistics, all doing tasks that aren’t the mission, but that are mission-critical. Without them, the car ain’t moving, the body ain’t bumbling.

In a computer there are all those low-level things going on, before you even have a browser window up to view a blog post. There’s the pre-OS stuff that loads up the OS, and that has its low-level bits before you get a user environment, and only once you have a whole set of disk and IO and network and drivers that can talk to all the various bits, only after everything is below can you put the windows on top and start asking for pages and rendering them.

In terms of economics, gaining population is about like gaining weight. You need extra support. More houses, more trash hauling, more power, more food. Shedding population means some of that support goes away with the population.

The numbers between natural (birth and death) population changes aren’t exactly the same as immigration and emigration. The natural versions have some extra services that artificial changes don’t, like hospital use, while migration has its own services like shipping or lawyers, administrative judges, and immigration police forces.

Obviously not great for the economy, especially if it’s rapid. In prehistory civilizations collapsed because a critical population loss triggered the population-equivalent of a bank-run. It can be much worse to live in a formerly-populated area than living in an unpopulated area, as there is a lot of support structure there that can’t easily be converted.

Population can’t grow indefinitely, and can only shrink to zero, but a smart society talks about how to adjust its population before embarking on major changes.