"Risk" means surprise

6 PhilGoetz 22 May 2015 04:47AM

I lost about $20,000 in 2013 because I didn't notice that a company managing some of my retirement funds had helpfully reallocated them from 100% stocks into bonds and real estate, to "avoid risk". My parents are retired, and everyone advising them tells them to put most of their money in "safe" investments like bonds.

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Let's make a deal

-18 Mitchell_Porter 23 September 2010 12:59AM

At the start of 2010, I resolved to focus as much as possible on singularity-relevant issues. That resolution has produced three ongoing projects:

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In conclusion: in the land beyond money pumps lie extreme events

4 Stuart_Armstrong 23 November 2009 03:03PM

In a previous article I've demonstrated that you can only avoid money pumps and arbitrage by using the von Neumann-Morgenstern axioms of expected utility. I argued in this post that even if you're not likely to face a money pump on one particular decision, you should still use expected utility (and sometimes expected money), because of the difficulties of combining two decision theories and constantly being on the look-out for which one to apply.

Even if you don't care about (weak) money pumps, expected utility sneaks in under much milder conditions. If you have a quasi-utility function (i.e. you have an underlying utility function, but you also care about the shape of the probability distribution), then this post demonstrates that you should generally stick with expected utility anyway, just by aggregating all your decisions.

So the moral of looking at money pumps, arbitrage and aggregation is that you should use expected utility for nearly all your decisions.

But the moral says exactly what it says, and nothing more.

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Consequences of arbitrage: expected cash

5 Stuart_Armstrong 13 November 2009 10:32AM

I prefer the movie Twelve Monkeys to Akira. I prefer Akira to David Attenborough's Life in the Undergrowth. And I prefer David Attenborough's Life in the Undergrowth to Twelve Monkeys.

I have intransitive preferences. But I don't suffer from this intransitivity. Up until the moment I'm confronted by an avatar of the money pump, juggling the three DVD boxes in front of me with a greedy gleam in his eye. He'll arbitrage me to death unless I snap out of my intransitive preferences and banish him by putting my options in order.

Arbitrage, in the broadest sense, means picking up free money - money that is free because of other people's preferences. Money pumps are a form of arbitrage, exploiting the lack of consistency, transitivity or independence in people's preferences. In most cases, arbitrage ultimately destroys itself: people either wise up to the exploitation and get rid of their vulnerabilities, or lose all their money, leaving only players who are not vulnerable to arbitrage. The crash and burn of the Long-Term Capital Management hedge fund was due in part to the diminishing returns of their arbitrage strategies.

Most humans to not react to the possibility of being arbitraged by changing their whole preference systems. Instead they cling to their old preferences as much as possible, while keeping a keen eye out to avoid being taken advantage of. They keep their inconsistent, intransitive, dependent systems but end up behaving consistently, transitively and independently in their most common transactions.

The weaknesses of this approach are manifest. Having one system of preferences but acting as if we had another is a great strain on our poor overloaded brains. To avoid the arbitrage, we need to scan present and future deals with great keenness and insight, always on the lookout for traps. Since transaction costs shield us from most of the negative consequences of imperfect decision theories, we have to be especially vigilant as transaction costs continue to drop, meaning that opportunities to be arbitraged will continue to rise in future. Finally, how we exit the trap of arbitrage depends on how we entered it: if my juggling Avatar had started me on Life in the Undergrowth, I'd have ended up with Twelve Monkeys, and refused the next trade. If he'd started me on Twelve Monkeys, I've had ended up with Akira. These may not have been the options I'd have settled on if I'd taken the time to sort out my preferences ahead of time.

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Money pumping: the axiomatic approach

12 Stuart_Armstrong 05 November 2009 11:23AM

This post gets somewhat technical and mathematical, but the point can be summarised as:

  • You are vulnerable to money pumps only to the extent to which you deviate from the von Neumann-Morgenstern axioms of expected utility.

In other words, using alternate decision theories is bad for your wealth.

But what is a money pump? Intuitively it is a series of trades that I propose to you, that end up bringing you back to where you started. All the trades must be indifferent or advantageous to you, so that you will accept them. And if even one of those trades is advantageous, then this is a money pump: I can charge you a tiny amount for that trade, making free money out of you. You are now strictly poorer than if you had not accepted the tradesat all.

A strict money pump happens when every deal is advantageous to you, not simply indifferent. In most situations, there is no difference between a money pump and a strict money pump: I can offer you a tiny trinket at each indifferent deal to make it advantageous, and get these back later. There are odd preference systems out there, though, so the distinction is needed.

The condition "bringing you back to where you started" needs to be examined some more. Thus define:

A strong money pump is a money pump which returns us both to exactly the same situations as when we started: in possession of the same assets and lotteries, with none of them having come due in the meantime.

A weak money pump is a money pump that returns us to the same situation that would have happened if we had never traded at all. Lotteries may have come due in the course of the trades.

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Dead Aid

1 PhilGoetz 17 March 2009 02:51PM

Followup to So You Say You're an Altruist:

Today Dambisa Moyo's book "Dead Aid: Why Aid Is Not Working and How There Is a Better Way for Africa" was released.

From the book's website:

In the past fifty years, more than $1 trillion in development-related aid has been transferred from rich countries to Africa. Has this assistance improved the lives of Africans? No. In fact, across the continent, the recipients of this aid are not better off as a result of it, but worse—much worse.

In Dead Aid, Dambisa Moyo describes the state of postwar development policy in Africa today and unflinchingly confronts one of the greatest myths of our time: that billions of dollars in aid sent from wealthy countries to developing African nations has helped to reduce poverty and increase growth.

In fact, poverty levels continue to escalate and growth rates have steadily declined—and millions continue to suffer. Provocatively drawing a sharp contrast between African countries that have rejected the aid route and prospered and others that have become aid-dependent and seen poverty increase, Moyo illuminates the way in which overreliance on aid has trapped developing nations in a vicious circle of aid dependency, corruption, market distortion, and further poverty, leaving them with nothing but the “need” for more aid.

From the Global Investor Bookshop:

Dead Aid analyses the history of economic development over the last fifty years and shows how Aid crowds out financial and social capital and directly causes corruption; the countries that have caught up did so despite rather than because of Aid. There is, however, an alternative. Extreme poverty is not inevitable. Dambisa Moyo also shows how, with improved access to capital and markets and with the right policies, even the poorest nations could be allowed to prosper. If we really do want to help, we have to do more than just appease our consciences, hoping for the best, expecting the worst. We need first to understand the problem.