Can You Short the Apocalypse?

August 12, 2017
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If the probability of nuclear war just went up why isn’t the stock market down? The stock market also didn’t fall during the Cuban Missile Crisis, as Lars Christensen points out:

If indeed we were on the brink of a nuclear exchange, one would certainly have expected the stock market to drop like a stone. Nothing of the sort happened. Instead, the S&P500 was little changed during the 13-day standoff between the United States and the Soviet Union.

Lars argues that the market must have figured out that MAD was a brilliant policy and thus the nuclear risk wasn’t anywhere near as large as most people thought (and nuclear war didn’t happen so the markets were right, right?)

Historian Arthur M. Schlesinger Jr., who was in the White House at the time, thought the Cuban Missile Crisis was the “most dangerous moment in human history.” None of the participants thought it was a yawn. I am inclined to accept their judgment. So why didn’t the market drop like a stone? It’s not so obvious that the apocalypse is priced into the stock market.

Let’s remember why markets are good at forecasting events. If you think IBM’s dividends are going to fall then you sell IBM stock and the fall in price signals the future event. But what do you do with the proceeds from the sale of IBM stock? You buy some other asset. Since IBM is only a small share of the market there are lots of other assets to buy.

If you think a nuclear war is likely, and you sell your stocks, what do you buy? It’s pointless to buy other assets like bonds–the bond markets probably won’t exist. You could buy land but who will enforce your property right? Even cash might be useless following a nuclear war. Maybe some gold coins and canned goods would be useful but you may not be around to enjoy them.

If the apocalypse really is coming your best bet is to cash out and spend it all now. But really how much fun would that be? Sure, you could have a great week of hookers and coke but I suspect a lot of people might prefer the cheaper option of a walk in the forest.

If the apocalypse were coming, I would have a second helping of chocolate cake and maybe a third helping but utility diminishes. Since utility diminishes you get a lot less enjoyment by consuming all your wealth now than by spreading it over a lifetime.

Diminishing marginal utility means that the optimal strategy to meet the apocalypse is very costly. Suppose you expect IBM dividends to fall and so you sell your IBM stock and use the proceeds to buy something else. If IBM dividends don’t fall, you haven’t lost much. But if you expect a nuclear war, cash out and blow it all, then you’ve lost a lifetime of consumption in return for a momentary buzz.

The bottom line is that selling stock doesn’t really help you to deal with a nuclear war or even to improve your life much before the nuclear war happens. The problem isn’t markets. An information market could still be used to produce information about the probability of a nuclear war it’s just that I wouldn’t necessarily expect that probability to correlate with the broader markets. Since any actions you might take in the broader markets are fruitless or very high cost, knowing that the probability of a nuclear war has increased is mostly useless information. You might as well ignore useless information and proceed to buy and sell stock as if the information didn’t exist.

You can’t short the apocalypse. As a result, I am not much comforted by the fact that markets appear steady in the face of apocalyptic risk.

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