Saturday, June 27, 2015

New World, Non-Malthusian Population More Determined by Historical Accident Than Climate

Above: the Frontier Strip - the westernmost U.S. states before the Rockies - contain the 100th meridian (bold vertical line in maps) which is often used a marker of low precipitation and therefore low agricultural productivity. The argument has been that the population therefore drops off to the west of this; but if that's the case, then why does Canada not follow the same pattern?

It is commonly believed that the population drop-off seen in the United States at the 100th parallel has to do with changes in rainfall and agricultural productivity as one moves west in North America. This article shows that this is probably not the case. It more likely has to do with historical accident - about the time Americans had expanded west to the 100th meridian, we started building trains, and people could move to the more pleasant climates of the West Coast. Note that the "population distribution is by historical accident" theory applies more to the New World than the Old, because of the introduction of intensive agriculture and lack of a Malthusian limit. Maybe over time, there will be a smoother population gradient - it would be easier to argue that with thousands of years of agriculture, longer-term Malthusian limited populations in Asia and Africa populations do reflect agricultural productivity, and therefore also rainfall and longitude-degrees from ocean.

Presumably the same applies to latitude, although for different reasons. Very high latitudes are not great places to grow food. Latitude is still going to be affected by geography (if you're near coastline at 25 degrees latitude, life is much more pleasant than if you're inland) - but the solar radiation remains constant so the effect of latitude is a little less subject to being obscured by the details of geography than longitude would be. (Note that there may be constraints on population growth other than calories that I'm completely neglecting; e.g., maybe agriculture at the equator is better than 30 degrees, but disease slows population growth once you drop below the 30s.)

Geography junkies have likely already seen maps like the one above showing population by latitude, and the assumption is that agriculture just produces more calories at certain latitudes (similar to the provincial precipitation distribution that obtains in North America and which was assumed to influence our own population distribution). But if we're trying to pull out first principles, absolute population doesn't help much - what if there's just a lot of land at certain latitudes? That doesn't tell us whether that latitude is good for agriculture and therefore modern humans, it tells us where the land is on Earth's surface. If your denominator for population density includes ocean, then it doesn't really tell us anything about the carrying capacity of land at that latitude. So population alone won't work - it needs to be population density.

And even just population density per latitude won't work - it has to be population density per actual land area found at that latitude. I couldn't find population density per land area data. Fortunately this Brookings Institute Paper quotes World Bank 1997 figures for land area and population in bands of 10 degrees latitude (see pp 49-51), and I back-calculated population density per actual land area at this level of granularity.

Thinking it might be interesting to see how things stack up when the northern and southern latitude bands are combined, I did so:

(There wasn't full data below 40s south or above 50s north, which means we can't even do 50s when we combine them, which non-ideally eliminates most of Europe.) The question that emerges is, what's wrong with you people in the 30s and 40s south? Up here on the correct side of the world we certainly seem to be able to get along alright in those latitudes. The lion's share of the land in the 30s and 40s south is to be found in the southern half of Australia, most of Argentina and Chile, and South Africa. These aren't bad places to live - note that this contains 3 of the world's 5 Mediterranean climate zones! Again, even trying to smooth things out, historical details matter. These are places where intensive agriculture was only introduced in the last few centuries by Europeans. And geographical details matter, even after using population density instead of population - Australia is an ancient craton with terrible soil, and Argentina is drier than it might otherwise be due to the rainshadow of the Andes. That said, in the Malthusian future, we should expect to see the Pampas filling up much like another Mediterranean climate zone (California) is filling up as we speak.

Finally, it's worth glancing at Malthusian long-term intensive agriculture countries, to see whether this holds up. I've put population density, precipitation and elevation next to each other. China's marked parallels are 40-30-20. India's are just 30-20. (10 crosses near the southern tip of the subcontinent.)

The precipitation relationship holds up better for India than for China, but both of them follow elevation. This may be more true in rice-farming areas than other grains. The relationship of population to elevation has been profitably studied elsewhere; there's a notable outgroup in the central Mexican plateau, where grains that enjoy dry conditions are grown and near to where agriculture began in North America.

Fully stated then, the theory can then be summarized as "Population distribution is strongly influenced by agriculture which in turn is determined by climate and therefore latitude, but a) until Malthusian limits are reached millennia after the introduction of intensive agriculture, distribution will be mostly by historical accident as in the New World and b) precipitation and especially elevation dramatically affect the distribution as well."

Tuesday, June 23, 2015

Books I Read in 2013-2014

At first I thought the exercise of posting book lists was middlebrow vanity but it actually does help to organize your thinking and retain what you've read (the best is to write a review on each). I should note that a number of these were abandoned ("liberated") partway through (mostly fiction). For some reason people hesitate to notice and act on the sunk cost fallacy when reading, but it's a virtue to walk out of a bad movie, even when you've paid!

Also Spracht Zarathustra - Nietzsche
Herodotus - the Histories
Kama Sutra
Just So Stories - Kipling

Moonwalking with Einstein - Foer
Willpower - Baumeister and Tierney
Predictably Irrational - Ariely
Rational Choice in an Uncertain World - Hastie
Thinking and Deciding - Baron

Neural Darwinism - Edelman
Man's Search for Meaning - Frankl
Mind Over Mood - Greenberger/Padesky
Handbook of Cognitive Behavioral Therapies - Dobson
First Aid for the USMLE Step 2 CK
Crush Step 2
Cases for the USMLE Step 2 CK
Q&A for the USMLE Step 2 CK
Step Up to Medicine

Olympos - Dan Simmons (This one I can review: I hated it. I hated it from page one and kept hating it so much.)
Zulu Heart - Stephen Barnes
A Heavy Metal Memoir - Dave Mustaine

Memorable Short Story Writers (most of whose stuff I sought out online after reading one story)
Yoon Ha Lee
Ted Chiang
Ken Liu

Alternate Histories: Russian Hawai'i, Swedish Delaware

Actually, it sounds like alternate history but it's not:

"In 1815-17, Kaumuali'i led secret negotiations with representatives of the Russian-American Company in an attempt to gain Russia's military support against Kamehameha; however, the negotiations folded and the Russians were forced to abandon all of their presence in Kaua'i, including Fort Elizabeth, after it was revealed that they did not have the support of Tsar Alexander I."

More here - perhaps, even stranger to my American eyes and ears than the 17th century Swedish colony in Delaware. I would think some fascinating alternative history could be written about either of these, but like all fiction, alternative history is about us, here and now, and here and now we don't think much about the Russian and Swedish forays into Hawaii and Atlantic North America (although there's online discussion of Russian Hawai'i of course, here's an online crack at a surviving New Sweden...)

I only just discovered the Points of Divergence alternate history site, which I will surely be wandering around in the coming days.

Monday, June 22, 2015

Hobbes Understood Why It May Be Rational in Unstable States to Heavily Discount the Future

"In [the war of all against all], there is no place for industry; because the fruit thereof is uncertain."
- Thomas Hobbes, Leviathan, Chapter XIII, "Of the Natural Condition of Mankind as Concerning Their Felicity and Misery"

More on the rationality of future discount rates in Japan and Somalia here.