NetLogo Models Library:
This model demonstrates a very simple bidding market, where buyers and sellers try to get the best price for goods in a competitive setting.
The agents in the inner ring of represent sellers, who bring some goods they want to sell to the market. The agents in the outer ring are the buyers, who bring money to the market to buy the goods.
Each round (tick), the buyers move to their right (counter-clockwise) and are paired with a seller. Then each buyer checks its paired seller's asking price. If it's lower than their asking-price, they'll buy 1 item. If it's higher, they'll buy nothing. Then each seller individually decides to either raise prices or lower prices based on their buyer's behavior. The buyers also individually lower or raise their expectations based on their seller's behavior.
The market will run through rounds until no buyer who wants to buy an item has money left to spend, or until all items are bought.
If a purchase is made, the link from seller to buyer turns yellow and a little star animation will start. Otherwise, the link will be blue with no animation. If the transactions still take place too quickly to be noticed, the speed slider can slow the model down a bit.
As buyers get what they want, they get bigger and fill their maximum-buy-sized gray shadow. If they fully satisfy their demand, they'll turn dark grey.
Sellers start with a size based on how many items they brought to the market. As they sell items, they get smaller. If they sell all their items, they'll turn dark grey.
Press SETUP to generate a market, then the GO-ONCE button to run a single round, or the GO button to run the market until it completes.
Try slowing the tick speed down and watching a single buyer on the outside ring as it moves. See how it gets bigger when it makes a purchase and its link turns yellow, and how big it is when it turns completely dark grey (if it does).
Run the model multiple times with the same settings to get an idea of what's happening to the asking and buying prices over time.
Play around with the different setup options to try the following:
It's fairly easy to add new behaviors to buyers and sellers, just adjust the chooser box with a new option, then add it in the appropriate
create-ordered-buyers block in the setup procedure.
In order to try to keep the Asking Price and Buying Price plots displaying relevant information, we set the
plot-y-range manually using an update command based on the most recent average price.
Behaviors for buyers and sellers are set during setup, and we use anonymous procedures stored in turtles-own variables. This allows us to very easily execute different behavior while the market is running by just using the
run keyword with those behavior variables.
See the Simple Economy model or Sugarscape models to explore other economic concepts.
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For the model itself:
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Copyright 2017 Uri Wilensky.
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