Extended weekend links

1) How to design things in a way that defends a billion people’s minds from getting hijacked.

2) On driverless trucks and universal basic income.

3) Is the Macroeconomy Locally Unstable and Why Should We Care?

4) “The most dramatic moment of learning in my life happened in less than a second. And that was sticking my head in the water at Shemya Island,” Estes recalled. “We were in this sea of just sea urchins. And there was no kelp anywhere. Any fool would have been able to figure out what was going on.”

5) Why not just buy out the US coal industry?

6) "We also turned up significant racial disparities, just as Holder feared. In forecasting who would re-offend, the algorithm made mistakes with black and white defendants at roughly the same rate but in very different ways."

7) Ridership on the New York City Subway accounts for all of the transit increase since 2005.

8) We need a species-wide conversation about the future of human genetic enhancement.

9) "We find that expansions of transportation networks have significant health costs in increasing the spread of viruses."

10) "Many of our expert epigenetics research colleagues are deeply embarrassed by the warm, uncritical response their work has attracted from the social sciences,"

11) In the early 1990s recovery, 125 counties combined to generate half the total new business establishments in the country. In this recovery, just 20 counties have generated half the growth.

12) "Without a model as a fortification, we found ourselves rambling around the countryside like all the other pundit-barbarians, randomly setting fire to things."

13) "Taken together, the combination of sorting and bargaining effects explain about one-fifth of the cross-sectional gender wage gap in Portugal."

14) An analysis of Jevon's salad: "It takes around 23 kg of fossil fuels for us to produce 1 kg of lettuce."

15) "We’ve been running TPUs inside our data centers for more than a year, and have found them to deliver an order of magnitude better-optimized performance per watt for machine learning. This is roughly equivalent to fast-forwarding technology about seven years into the future (three generations of Moore’s Law)."

16) Are guns and knives substitutes?

17) "The long-term consequence of such effects is an expected genetic deterioration in the baseline human condition, potentially measurable on the timescale of a few generations in westernized societies, and because the brain is a particularly large mutational target, this is of particular concern."

18) Josh Angrist has some very nice regression recap slides in the Mostly Harmless Big Data course on MIT OCW

19) Virtual reality and the nonhuman lived experience

20) "Three years ago, turf cutters in Ireland’s Offaly county found over 100 pounds of bog butter inside a keg. It was estimated to be 5,000 years old."


The effect of legal ivory sales on elephant poaching

Nitin Sekar and I have a new paper out today on the effect of large-scale legal international sales of ivory designed slow poaching of elephants. The basic theory is that these sales should flood black markets, depressing the price of ivory and reducing the incentive to poach. We point out that these sales might also attract new consumers of ivory (who were unwilling to buy it when it was illegal but are interested in ivory when it becomes legal and sheds the stigma of contraband) and/or make it easier to smuggle illegal ivory (because it's easier to pretend that illegal ivory is legal once there is legal stuff floating around). Under the right conditions, these two effects can overpower the "market flooding" effect that policy was targeting, causing a legal sale to backfire and actual generate more poaching than before thee sale. This seems to be what happened when there was a large experimental sale announced in 2008:

Here's the paper and abstract:

Does Legalization Reduce Black Market Activity? Evidence from a Global Ivory Experiment and Elephant Poaching Data
(Solomon Hsiang and Nitin Sekar)
Abstract: Black markets are estimated to represent a fifth of global economic activity, but their response to policy is poorly understood because participants systematically hide their actions. It is widely hypothesized that relaxing trade bans in illegal goods allows legal supplies to competitively displace illegal supplies, but a richer economic theory provides more ambiguous predictions. Here we evaluate the first major global legalization experiment in an internationally banned market, where a monitoring system established before the experiment enables us to observe the behavior of illegal suppliers before and after. International trade of ivory was banned in 1989, with global elephant poaching data collected by field researchers since 2003. A one-time legal sale of ivory stocks in 2008 was designed as an experiment, but its global impact has not been evaluated. We find that international announcement of the legal ivory sale corresponds with an abrupt ~66% increase in illegal ivory production across two continents, and a possible ten-fold increase in its trend. An estimated ~71% increase in ivory smuggling out of Africa corroborates this finding, while corresponding patterns are absent from natural mortality and alternative explanatory variables. These data suggest the widely documented recent increase in elephant poaching likely originated with the legal sale. More generally, these results suggest that changes to producer costs and/or consumer demand induced by legal sales can have larger effects than displacement of illegal production in some global black markets, implying that partial legalization of banned goods does not necessarily reduce black market activity.


Potentially extreme migrations under climate change

Adam Sobel and I have a new paper on Potentially Extreme Population Displacement and Concentration in the Tropics Under Non-Extreme Warming.

The paper is a theoretical exercise making a simple point: tropical populations that migrate to maintain their temperature will have to move much further that their counterparts in middle latitudes. This results from well established atmospheric physics that aren't focused on by the researchers who usually think about climate change and migration. One reason this result is interesting is that, in a sense, the physics of the tropical atmosphere "amplify" the impact of warming (at least in this dimension) so that even small climate changes can produce really large population displacements in the tropics (theoretically).

Here's the abstract:
Evidence increasingly suggests that as climate warms, some plant, animal, and human populations may move to preserve their environmental temperature. The distances they must travel to do this depends on how much cooler nearby surfaces temperatures are. Because large-scale atmospheric dynamics constrain surface temperatures to be nearly uniform near the equator, these displacements can grow to extreme distances in the tropics, even under relatively mild warming scenarios.  Here we show that in order to preserve their annual mean temperatures, tropical populations must travel distances greater than 1000 km over less than a century if global mean temperature rises by 2C over the same period. The disproportionately rapid evacuation of the tropics under such a scenario causes migrants to concentrate in tropical margins and the subtropics, where population densities increase 300% or more. These results may have critical consequences for ecosystem and human wellbeing in tropical contexts where alternatives to geographic displacement are limited.
See my post here for a longer explanation of what's going on in the paper.


Financial market response to extreme events indicating climatic change

My article "Financial market response to extreme events indicating climatic change" just came out in the "Health, Energy & Extreme Events in a Changing Climate" issue of the European Physics Journal: Special Topics:
A variety of recent extreme climatic events are considered to be strong evidence that the climate is warming, but these incremental advances in certainty often seem ignored by non-scientists. I identify two unusual types of events that are considered to be evidence of climate change, announcements by NASA that the global annual average temperature has set a new record, and the sudden collapse of major polar ice shelves, and then conduct an event study to test whether news of these events changes investors’ valuation of energy companies, a subset of firms whose future performance is closely tied to climate change. I find evidence that both classes of events have influenced energy stock prices since the 1990s, with record temperature announcements on average associated with negative returns and ice shelf collapses associated with positive returns. I identify a variety of plausible mechanisms that may be driving these differential responses, discuss implications for energy markets’ views on long-term regulatory risk, and conclude that investors not only pay attention to scientifically significant climate events, but discriminate between signals carrying different information about the nature of climatic change.
The paper is here, and note that the rest of the issue includes an overview of the climate and conflict literature by Sol, Marshall Burke, and Tamma Carleton, as well as Gordon McCord's article forecasting climate change's influence on malaria ecology.