Thanks to some very good points made by wakaba I've decided to write a followup post.

More cash is always worth more than less cash. Rationally trading two differing amounts of the same currency is thus impossible. A stock has risk; its future dividend is not guaranteed. Estimating the value of a stock involves constructing a probability distribution for the future stock dividends.

Different people have different information, and may thus infer different distributions. However, even when they have the same beliefs and infer the same distribution, they will still price the stock differently depending on their differing appetites for risk. For example, a grad student would be willing to pay less than a millionaire for the same 50% chance at winning $10,000. See also the St Petersburg Paradox.

A corollary of this line of logic: given that two people infer the same probability distribution A, they will arrive at the same price for the stock as the uncertainty of A becomes smaller and the appetite for risk becomes irrelevant.

I would like to see a comparison one of these days between nations and open source projects in terms of how they are governed. There is much variety amongst open source projects in systems of government, including consensus (subversion), voting (debian), and benevolent dictatorship (python).

The video features lead developers from the subversion project, which has a consensus based community. During the presentation, they state that voting should be a last resort.

"If you find yourself voting on everything all the time then something is wrong, and you need to be more introspective. Voting means there is a winner and a loser ... People need to learn how to make compromises, and hopefully you are bringing people into your community who are the kind of people who like to make compromises and are willing to deal with that."

This is a gem of a comment to me, because it encapsulates so much of what I think is the problem with many communities - the lack of a common desire for sincere consensus. Many other significant points like this one are discussed, and I highly recommend watching the video.

I've been reading What is Thought? by Eric Baum, a book on the mind by an AI researcher.

For part of the book, Baum describes solving Blocks World problems with a computational economics model. The problem is called Hayek, and it is described in this article. I will just describe the part that is most interesting to me.

The program is implemented as a collection of agents which bid for ownership of the puzzle. Only the owner of the puzzle at any given time is allowed to move its pieces. The puzzle itself is turned into a cash reward when it is solved. Otherwise the world is zero-sum between agents, with money only changing hands during the sales of the puzzle between agents.

Using such rules, evolutionary algorithms are applied to encourage the development of more profitable agents. Successful agents were those able to buy low and sell high, which (assuming accurate pricing) would mean being able to advance the solution the most.

Of course, accurate pricing is a hairy issue; the hardcoding of a good scoring function helps the system a lot.

This is a general parallelization paradigm, where heuristics exist in ecosystems which estimate the value of each other's actions and compete to maximize their own value in that context. An agent's pricing of the puzzle state is subjective to the extent that it is specific to the position of that agent's actions in the chain leading to the solution, and objective to the extent that the other agents see the same chain. I would guess that it is more objective when the action chain is serial and more subjective when many alternative parallel chains exist.

I find Economic AI models cool because they clearly work for humans, and if could be made to work for computers would allow the construction of hybrid cybernetic economies where humans and agents can compete in the same pool.