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 >
============================================================ 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
