Alida Addis, Maurizio Fiumara

Computer Science and Simulation for Economics

Project work on

"Workers in a grey economy."


The applet requires Java 1.4.1 or higher. It will not run on Windows 95 or Mac OS 8 or 9. Mac users must have OS X 10.2.6 or higher and use a browser that supports Java 1.4. (Safari works, IE does not. Mac OS X comes with Safari. Open Safari and set it as your default web browser under Safari/Preferences/General.) On other operating systems, you may obtain the latest Java plugin from Sun's Java site.

created with NetLogo

view/download model file: workers_ in_a_ grey_economy.nlogo


The model faces the theme of black economy in contrast with regular workers.

There are three important moments that model represents:

1. balance, in which there are no unemployeds;
2. workers looking for black moonlighting;
3. dismissals.


The model begins with a number of unemployeds that move in the direction of the firms.
Each white "agent" goes towards colored firms to try job.
Each firm has an amount of production that depends by total demand.
If the agent finds job it changes color from white to the color firm and remain here.
If the worker expenditure are higher than his income, it try a black moonlighting. It hatch another agent with different shape and bigger size that begins his travel from start point towards colored firms.
If the production decreases, firm dismisses one or more workers; it depends by the difference between production and number of income distributed.


SETUP: clears the world and creates the number of turtles specified in the NUMBER slider.
GO-ONCE: runs the simulation step by step.
GO-FOREVER: runs the simulation continuously.
DEMAND: controls the total goods demand.
NUMBER: specifies the number of turtles created in SETUP.
ADD_EXPENSE: increase the range of random variable expenditure.
SHOW_EXPENDITURE: shows the single agent value of expenditure.
SHOW_CASH: shows the single agent value of cash.
SHOW_SAVING: shows the single agent value of saving

There are also two plots called respectively "Labor force" and "Workers per firm" that displays, over time, the number of turtles unemployeds, workers and illegals and how much of them work in each firm.


The colored parts of the world represents the firms.
Each of the sliders has a different effect on the simulation.
For example, ADD_EXPENSE increase or decrease the range of variable expenditure.
Over time the hirings will depend by total demand controlled by slider Demand.
The four monitors on the bottom of the interface (UNEMPLOYEDS,REGULARS,TRYING and ILLEGALS) represent the distribution of the individuals at a given time.

What effect does an increase in ADD_EXPENSE generally have on looking for black moonlighting?
And what effect does an increase in demand generally have on dismissals?


Vary the ADD_EXPENSE as the model runs and watch the effect this has on looking for black moonlighting.

Start specifying five turtles in NUMBER slider: you can see run the cooperative only (I mean turtles with links)


In this model exists one level of hiring only. Try extending the model to more levels.


Most NetLogo models put the origin (0,0) in the center of the world, but here, we have placed the origin near the bottom edge of the world. Simply as visual effect.

Vertical wrapping is enabled, but horizontal wrapping is disabled. Thus, the world topology is a "horizontal cylinder".