Why do economists fail at basic math?

In “Open Borders and the Hive Mind Hypothesis,” economist Nathan Smith writes:

“Open borders, in the sense of the abolition of policies restricting migration, would cause billions of people to migrate, and result in almost a doubling of world GDP. Based on a model that stresses human capital as a determinant of the wealth and poverty of nations… two openborders scenarios are constructed. In the first, “pure market clearing” scenario, world GDP rises 91% as 82% of the world’s population migrates, mostly to the West … In the second scenario, with several adjustments made to favor greater realism at the expense of some arbitrariness, world GDP rises 85% as 58% of the world’s population migrates…”

Jesus effin’ Christ. According to Google, there are 7.3 billion people on the planet. About 1 billion of them live in the West/1st world nations. About 6.3 billion of them live in “developing countries.” I’d calculate average population density of the West, but places like Australia (90+% desert) and Russia (Siberia) have big chunks of very difficult to live on land that would render the calculation meaningless. However, it is pretty easy to grok that the population density of Europe and Japan, especially relative to its arable land, is already pretty darn high:

Rush hour on the Tokyo Subway

 

Shibuya Station, Japan

 

Somewhere near NYC, I believe

 

Parisian apartment complex

So forgive me if I think the idea of cramming 5.17 billion people into the first world actually sounds horrific. Where would you put everyone? How would you feed them? Surely not with crops grown by people on newly freed-up land back in Africa–folks with a TFR of 7 or 8 aren’t going to stop having babies just because they suddenly got the resources to feed more of them. Africa’s population will stay the same.

Even the more modest scenario implies the immigration of 3.65 billion people, resulting in a quadrupling of the West’s current population.

I don’t care what your model shows. This is a recipe for destroying the planet.

Of course, there are factors other than GDP to consider. Like total arable land, crime rates, or having a pleasant community full of people you like and trust–but these are not factors that economists consider valid. We must sacrifice all to the mighty GDP.

 

Later in the article, he admits that all of his models are based on total assumptions about the way wealth is generated (having dealt with humans, I suspect that assumption is “magic,” but I could be wrong,) and that other models actually show a 25% reduction in global GDP under open borders. This is fine, of course, because someone else might benefit. I mean, not you. You’ll probably starve to death in a smog-ridden hellscape.

For that matter, if you really want to alleviate poverty, you can just give 25% of your income directly to the third world, and then no one has to go through the expense and trauma of moving. I seem to remember a post on Slate Star Codex arguing that it was more effective to just build houses for people in Africa than to ship people to Sweden and then build houses for them there, but now I can’t find it. Maybe it was a different blog? Either way, the point stands: there are probably better ways to raise up the bottom end of society than crashing the whole system.