Wednesday, January 22, 2014

Altitude and Population Density

Cross-posted to my outdoors blog,

We typically go to mountains to get away from it all, especially other humans. I'd always wanted to investigate the relationship between population density and elevation. Surprise! Such a relationship exists. The higher you go, the lower the density; in fact the relationship is even stronger than exponential. Even more interesting than that is understanding why. But first: figure below is from Cohen and Small 1998:

Note the bump at 2,300 m and again at 4,000+. 2,300 is mostly people on the Mexican Plateau, and 4,000 is Tibet + the Andes.

I plugged in data just for ~250 cities in the state of Utah, and got a worse R^2 than I saw for Cohen and Small's data (0.25 vs >0.9 for theirs), but this isnt' that granular; when I tried to do the same thing using mean elevations and population densities for the 50 states it was a mess. I think it would work a lot better at the county level.

So why is this? You might be tempted to speculate that it has to do with the limits of human physiology. That is to say, the higher you go, the more uncomfortable people are (thin air, cold) and the less adaptable, right? It's hard to imagine (for example) that Las Vegas at 665 meters would be a more comfortable place at a lower elevation. And physiologically, as it turns out, in the second half of the twentieth century medical anthropologists studied people in Tibet and the Andes extensively for their physiological adaptations to altitude - the underlying mutations for which have now been characterized (and in the Tibetan case have all occurred in the last 3,000 years!). But the idea that a few hundred meters of elevation will start impacting physiology and population growth falls apart both in terms of common sense and as a direct implication of other work. Any decrease in fertility caused by altitude would cut right at population growth - but this turns out not to be a big concern even for Himalayans living much higher.

You could also argue that the world's large cities tend to be seaports, which are at low elevation, so it's ease of transportation that gives us this bias toward lower elevations; but this is more true for New World that got settled by the sea than the Old World that got settled by land, and people must be pretty lazy if what's keeping them at sea level is their ancestors having gotten off a boat there a few centuries ago.

Terrace farming in the Himalayas.
I bet they would rather just have flat fields.

Beyond some historical accidents, the answer is likely to be mostly "agriculture". The overall population distribution we see in the world today basically reflects how early people in a certain part of the world adopted agriculture and how effective it was, given the crop and the climate, and escaped the Malthusian cycle; hence the highest densities being in a band running from east, southeast, and south Asia. The Middle East started early and although the marginal environment was also a driver for state formation, it was still marginal, and the Fertile Crescent just can't compete with the Ganges or the Pearl River. (So it can be accurately said that on average, humans are Asian; hence this map). So the relationship between elevation and population is really about where agriculture is better, and it's better at lower elevations for many reasons. Otherwise it's hard to understand the Mexican bump at 2300 meters, where (guess what) agriculture was first invented in the New World.

So, if someone ever thinks of a way to do agriculture as easily in the mountains as on flat lands, the days of undeveloped remote mountains are over.


Cohen JE and Small C. Hypsographic demography: The distribution of human population by altitude. Proc. Natl. Acad. Sci. USA, Vol. 95, pp. 14009–14014, November 1998.

Goldstein MC, Tsarong P, Beall CM. High Altitude Hypoxia, Culture, and Human Fecundity/Fertility: A Comparative Study. American Anthropologist 85(1), March 1983.

Saturday, January 18, 2014

"Small Government" Conservatives Forget States Rights When Marijuana is Legalized

Ted Cruz and social-conservative (read "fake") libertarians want to use government to force people to follow their moral code. Most of the time they think the state government is the way to encourage freedom, when (curiously) state governments are limiting freedom - of abortion, of religion, you name it. But when the state governments don't do what they want, well then, the Federal government is a-okay!

Wednesday, January 15, 2014

Losing to Specialists, and Competing for Attention

Economist Tim Harford has a short and pithy post, comparing some aspects of the modern consumer's experience to being in a casino. Specifically, he notes that the complex agreements that we have with (for example) cloud-connected devices are often so confusing as to be maze-like - exactly like a casino's interior, so you're less likely to act on your impulse to leave. (If you've ever stopped at a casino just to use the bathroom and spent five bewildered minutes wandering in the interior, you know what I mean.) It's been noted previously that in a complex modern economy, specialization is required - and since the consumer doesn't have the same level of understanding of their (real estate transaction, mobile device, etc.) as the specialist, there is an information asymmetry that damages modern market's efficiency.

In the same post Harford also notes the competition for attention that is increasingly part of our economy, most obviously online.

Saturday, January 11, 2014

How to Become Dominant During the Twentieth Century

Reproduced from the Economist, originally from Thomas Picketty's Capital in the Twenty-first Century

It is difficult to overstate the geopolitical impact of the destruction of European capital during the World Wars. Note that the graph here is capital as a share of national income. The European countries represented are now back to pre-war levels, and higher than the U.S., but it's the rate of capital loss (and the implied shock) that is most salient.

As with most things, America's narrative of its own success is more complicated than boosters or detractors would claim. One factor that absolutely helped the U.S. surpass its competition was that it is on a separate continent than its competition, so when wars broke out, they flattened each other twice in less than half a century, leaving the U.S. mainland unscathed. (Even Australia came in for worse treatment in the Second World War with repeated Japanese bombing runs on the mainland.) Probably because this was mostly the result of geopolitical good luck rather than any decisions America's leadership made, or America's cultural values or institutions, this part of the narrative is grossly under-emphasized.

Saturday, January 4, 2014

Dunbar's Number and Startup Companies, Part 2

Many people have noted and describe the culture shift that occurs at startup companies - curiously, usually at a headcount right around Dunbar's number. Of course, differences occur over the causes.

One explanation from personal experience as a consultant at multiple companies (full post here) is that the influx during this growth phase consists mostly of people who are middle- or lower-tier contributors, whose strategy is primarily that of seeking a stable institution and burrowing in. This is a rational strategy for these folks, because as the company grows, the individual's contribution (especially the lower-level, later hires) is less important to the company's health and therefore feeds back less to the individual's fortune. There's no reason to knock yourself out, if you know it won't make much difference to your future well-being, and you don't have confidence in your talents anyway.

(When aggressive young managers talk to these people, it sometimes feels like you're playing two different games on the same field. Manager is rewarded by scoring. S/he wants to perform, and wants others to perform, so risk-taking and occasional annoying of others with non-company-aligned-goals is worth it. Late-comer wants to keep a low profile and not rock the boat and often seems frankly confused at any suggestion that they should take a risk to accomplish something, but of course s/he can't say this out loud. Or sometimes, they actually do. I once had an employee, a recent college grad, who looked at me with surprise at the start of such a meeting and said, "This isn't me, this job isn't what I really do." I was grateful for this honesty because it saved time. Not in the way that I think this employee was expecting.)

Netflix has a set of slides that's been making the rounds in the Valley recently, with a different (though not necessarily conflicting) explanation. This explains the dilution of high performers as an efflux of talent (driven out by bureaucratic process sclerosis) rather than the influx of low performers. This certainly occurs as well though in my experience, it's a much slower process, as people tend to stay at a company they believe in with colleagues they enjoy even as administrative annoyances accumulate.

I also think that they're being too kind about the motivations behind the proliferation of bureaucratic rules, which they ascribe to well-meaning management trying to control the chaos at a company that's become too large and complex to run informally. I think there's a lot more conscious justifying-of-one's-own-existence processes that new administrators put in place, although I concede this is easier to do and probably happens more in my regulation-heavy world of biotechnology than in the tech world that the Netflix people know.

Friday, January 3, 2014

If Every U.S. State That Tried to Secede From Another State Became a State

It would look like this. I'm now living in Reagan (I might actually be if the current petition to divide California succeeds). As for the place of my birth, it didn't change names although the lower three counties succeeded in seceding and are now called Delaware. Jerks. (Full on alternate history here; cool alternate geography here, here or here.)