P.S. In model, though, there are no gifts, only exchanges. And exchanges are made when one agent has something another agent needs. So I don't think that model applies, at least not in its simple form.
-- Russ Abbott _____________________________________________ Professor, Computer Science California State University, Los Angeles o Check out my blog at http://bluecatblog.wordpress.com/ On Sun, Apr 12, 2009 at 11:47 AM, Russ Abbott <[email protected]> wrote: > I'll have to look at the paper. But I'm surprised at the result. It seems > counter intuitive. If an agent has nothing, he can't give anything away. But > he has as good a chance to receive a gift as anyone else. So agents will > tend not to go below a basic minimal level. Agents with lots of wealth are > always giving it away. Yet they don't have a better change of getting any > new wealth than any other agent. So why should their wealth grow? It would > seem that wealthy agents would get wealthier only if wealth increases the > probability of getting a gift. But the model didn't seem to suggest that. > > I guess what might happen is that if wealth becomes concentrated, fewer > transactions (gifts) occur at each time step -- since only those agents with > any resources give gits. I.e., if lots of agents have nothing to give, > fewer gifts occur at any time step, and each agent has a smaller probability > of receiving anything. So if the distribution of wealth is such that the > expected value of an agent's wealth stash decreases at every time step (as > long as he has anything) then agent wealth stashes will tend toward zero. > But since the money doesn't disappear, it will accumulate in a few agents. > > So I guess the population will tend to a distribution in which the > percentage of agents with more than 0 units of wealth becomes constant at > the level of the probability that any agent will receive a gift. (Or > something like that.) That is, if every agent has one unit to give away, the > expected value of the number of agents who will have a unit after the > exchange is less than the total number of agents since some agents may > receive two gifts. If only one agent has something to give away (plus > something in reserve), the expected number of agents who will have something > after the exchange will be two since the receiving agent and the gifting > agent will each have something. So there must be a point at which the > number of agents with some wealth will be stay more or less constant. I'm > afraid I don't know how a Boltzmann distribution comes about. But I guess > it's something like that. > > -- Russ > > > > On Sun, Apr 12, 2009 at 11:16 AM, Stephen Guerin < > [email protected]> wrote: > >> Russ writes: >> >>> there are N agents; N resources are needed for survival. So if the >>> aggregate production is evenly distributed everyone has a subsistence >>> living. >>> >> >> I don't think this is necessarily true. >> >> Your mentioning a gift economy is further a reason to look at a model as >> simple as the Tom Carter/Victor Yakovenko model I mentioned where agents are >> giving a dollar to another random agent (ie gifting). This model, with >> minimal assumptions, generates non-equitable distribution of wealth where >> very few agents end up holding most of the wealth (Boltzmann distribution) >> even though the average wealth in the model is unchanged at $50/agent. >> >> The important constraint in the model is that agents can only have >> positive amounts of cash/goods -- they can't gift a dollar they don't have. >> >> Just as energy distributes itself as a boltzmann distribution as particles >> can not have less than zero energy after a collision (transaction). >> Basically we have diffusion against a wall in both models. Of course we can >> introduce debt and progressive taxes to the economic model to mess with the >> dynamics, but I think it's important to recognize the non-equity is there >> from the beginning with very minimal assumptions. Note that the wealthy >> agents do turnover in this model so the definition of what is equitable is >> important. >> >> -Steve >> >> >> >> >> On Apr 12, 2009, at 11:40 AM, Russ Abbott wrote: >> >> Thanks for all the responses. What prompted my question was thinking >>> about the "end state" of the current financial crisis. The question is: >>> what does a successful stable economy look like? Only secondarily was I >>> asking about markets, wealth distribution across society, etc., which is >>> what many of the existing models focus on. >>> >>> In attempting to describe the foundations of a stable economy I was >>> making the following assumptions. >>> • We live off the gift of free energy -- the sun. So in some sense >>> a stable economy requires little more than harvesting that energy. >>> • As human beings we have the innate (i.e., also free) ability to >>> transform that energy into other forms that we need. For example, most of us >>> on this list are capable of writing code. I'm taking skills like that as >>> more free gifts from nature. Yes, it requires, education, study, practice, >>> etc., but ultimately it grows out of our being alive, a free gift. >>> • In talking about "free gifts" from nature, I'm not trying to be >>> spiritual, new age-y, etc. It just seems to me to be the way the world >>> works. So I'm willing to build it into the model. >>> • But, even though we live off these free gifts, we all need >>> energy to survive. If you look at my "Reductionist blind spot" paper, you >>> see that we are what I call dynamic entities. Dynamic entities need to >>> import externally supplied energy to persist -- in our case food, at least. >>> So even though we find ourselves in a world in which there is externally >>> supplied energy available to be imported (from the sun and its stored >>> versions), we are each still required to do something to import it for >>> ourselves. That is, we must each work for a living. >>> • Presumably a standard economic model says that we live at a >>> subsistence level if the amount of work we do matches our needs. If I spend >>> all my working hours doing nothing more than earning what I need to survive, >>> that's subsistence. >>> • I want to allow specialization so I suggested that each agent >>> specializes in producing some resource but that the aggregate amount >>> produced exactly satisfies the needs of the producers. That is, each agent >>> produces N units of his specialty resource; there are N agents; N resources >>> are needed for survival. So if the aggregate production is evenly >>> distributed everyone has a subsistence living. >>> • A society/economy grows "richer" when it can produce enough >>> resources for itself without requiring everyone to work on producing those >>> resources. In that case, the available excess labor can produce >>> discretionary items, like art, pop music, software, soft drinks, philosophy, >>> etc. >>> • As technology advances a smaller and smaller percentage of the >>> population is needed to produce the necessities. The rest can spend their >>> time producing discretionary items. >>> • So at this point we are all well fed, and we are all willing to >>> spend our extra money supporting our local NPR stations. >>> • But what happens when there is shock to the economy and people >>> find that they have less "wealth" than they thought they had? Presumably >>> they will spend less on discretionary items, and the people who create those >>> items will be out of work. Where do we go from there? >>> So I am looking for a model to explore these kinds of issues. >>> >>> I must say that I'm surprised at the number of things I had to write down >>> to explain what I am after. I thought it would be simpler. And I want >>> something as simple as possible. >>> >>> Any thoughts/suggestions? >>> >>> -- Russ >>> >>> On Sun, Apr 12, 2009 at 9:14 AM, Victoria Hughes < >>> [email protected]> wrote: >>> > Attention and action = the price to consume. >>> >>> is it possible to have an idea / new information and not in some way, >>> internally or externally, react to it? >>> Memes spread. Humans by design infect each other on all levels. >>> The Complex seems like a great example: by definition intends to do this. >>> Idea / attention / action-reaction / experience / new idea. >>> And so forth. >>> Am enjoying the bouncing of ideas and information in this particular >>> string... >>> Tory >>> >>> On Apr 12, 2009, at 7:04 AM, Jochen Fromm wrote: >>> >>> The central property which emerges in markets is >>>> the price. The central law which rules markets is >>>> the law of supply and demand. A basic agent-based >>>> model for markets should explain how both, the >>>> price and the law of supply and demand, emerge >>>> in competitive markets. It should be simple to >>>> extend such a model to explain bubbles and crashes. >>>> As far as I know, there is no basic model of >>>> markets in general, there are only agent based models >>>> of specific markets, for example stock markets, >>>> financial markets and electricity markets. Perhaps >>>> the law of supply and demand is too simple to justify >>>> such a model? >>>> >>>> Epstein and Axtell's Sugarscape is a model where >>>> agents begin to accumulate "wealth" in some form, >>>> but it is more about evolution of societies and less >>>> about market mechanisms and economies. >>>> >>>> It would be interesting to apply a basic agent-based >>>> market model to the society of mind. If we consider the >>>> crowd within and the battle of ideas which is going on >>>> inside our minds, can we create an agent-based model >>>> to explain the 'market of information' ? We have a >>>> demand for new or highly emotional stuff, are constantly >>>> supplied with information from the outside, and the price >>>> we have to pay to consume it is attention. >>>> >>>> -J. >>>> >>>> ----- Original Message ----- From: Russ Abbott >>>> To: The Friday Morning Applied Complexity Coffee Group >>>> Sent: Sunday, April 12, 2009 9:00 AM >>>> Subject: [FRIAM] Agent-based market models >>>> >>>> Does anyone know of good examples of generic agent-based market >>>> economies? I'm thinking of something as simple as this. >>>> >>>> A population consists of agents each of which has certain continuing >>>> needs (such as food, clothing, shelter, Internet access, etc.) to survive. >>>> As a starting point, let's assume that each agent needs one unit of each of >>>> N resources every time period. Let's also assume that each agent is >>>> specialized and is capable of creating enough of one of the needed >>>> resources >>>> to satisfy the needs of N agents. (The fact that I used the same N in both >>>> places was intentional.) To keep it simple let's assume that these acts of >>>> creation occur from scratch, i.e., that the creator doesn't need raw >>>> materials, that all that's necessary for an agent to create a needed >>>> resource is that the agent be alive. The agents presumably develop a barter >>>> economy, trading the resources they create for the resources they need to >>>> stay alive. Perhaps markets develop, and perhaps money develops. At this >>>> point the economy should be fairly stable. Each agent creates enough stuff >>>> so that s/he can trade it for what s/he needs to stay live. >>>> >>>> Perhaps some of the agents learn how to be more efficient in creating >>>> their resource and begin to accumulate "wealth" in some form. Perhaps the >>>> agents have discretionary desires, which they fill if they have enough >>>> resources left over after meeting their basic needs. Perhaps there are >>>> communal services that are paid for by taxes or memberships. This could >>>> become increasingly elaborate. >>>> >>>> It seems to me that models of this sort must have been developed -- >>>> perhaps many times. Does anyone know of any references to this sort of >>>> work? >>>> >>>> Thanks. >>>> >>>> -- Russ Abbott >>>> _____________________________________________ >>>> Professor, Computer Science >>>> California State University, Los Angeles >>>> o Check out my blog at http://bluecatblog.wordpress.com/ >>>> >>>> >>>> ============================================================ >>>> FRIAM Applied Complexity Group listserv >>>> Meets Fridays 9a-11:30 at cafe at St. John's College >>>> lectures, archives, unsubscribe, maps at http://www.friam.org >>>> >>>> >>> >>> ============================================================ >>> FRIAM Applied Complexity Group listserv >>> Meets Fridays 9a-11:30 at cafe at St. John's College >>> lectures, archives, unsubscribe, maps at http://www.friam.org >>> >>> ============================================================ >>> FRIAM Applied Complexity Group listserv >>> Meets Fridays 9a-11:30 at cafe at St. John's College >>> lectures, archives, unsubscribe, maps at http://www.friam.org >>> >> >> >> ============================================================ >> FRIAM Applied Complexity Group listserv >> Meets Fridays 9a-11:30 at cafe at St. John's College >> lectures, archives, unsubscribe, maps at http://www.friam.org >> > >
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