Claudio Patrucco, Domenico Scarlato

Computer Science and Simulation for Economics

Project work on

"Population mobility in Italy."


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: mobility.nlogo


This project models the population mobility in Italy. Turtles' random movement depend on their mood, which is influenced by two variables: individual profit and environment. While the first one is constant (it doesn't change if popolation grows up or down in that area) and it is different for each area, the second one has an initial value which is the same for each area and it depends on the area's population.
Comparing the two values for each closed areas, turtles changes their mood if the closed areas have better values than the area where they are staying in that moment. In that case they begin to move till they will find out an area which has a good influence on their mood.

The Italian territory is been divided on 6 macro areas: North-East, North-West, Center, South, Sicilia and Sardegna


Click to SETUP button to set up the turtles and the patches. There is equal numbers of turtles and the same value of environment for each areas. Click GO so start the simulation. Is turtles are unhappy they begin to move till they will be happy again. if they move to the sea they will come back immediately on the earth.

The NUMBER slider controls the total number of turtles. (it takes effect the nest time you click SETUP.)
The P-OF-RANDOM-MOVE-UNHAPPY slider controls the probability of turtles' movement when they are unhappy.
The P-OF-RANDOM-MOVE-HAPPY slider does the opposite. The ENVIRONMENT slider controls the environment's value
for all the areas. The LIMIT-SPEED? slider controls the move's turtles speed.

The "population" monitors shows the number of people present on each areas. These monitors are also plotted.
The "number-unhappy" monitor shows the number of unhappy turtles.


When you execute SETUP, turtles are put on specific areas. All the turtles are "happy" but when you click "Go" the begin to compare their values' area with the closed ones area. If their area is not the best they begin to move out till they will find out a new "best" area. The environment variable has an important effect on the turtles' mood. Since its changes depend on the people present on that area, it determines the area's goodness. What I mean is that an area which can be the worst because of it is croweded, could become the best if all people moves away from there.

If the P-OF-RANDOM-MOVE-HAPPY is not equal to 0 you can see turtles move even thogh they are happy.


Try different values for P-OF-RANDOM-MOVE-HAPPY and P-OF-RANDOM-MOVE-UNHAPPY. How does the turtles' move change if the first probability is 0,8 nd the second one 0,2? What does it happen if P-OF-RANDOM-MOVE-HAPPY is 0,2 and P-OF-RANDOM-MOVE-UNHAPPY 0,8?

Try different values for all INDIVIDUAL_PROFIT and ENVIRONMENT. How does the turtles' mood change if the ENVIRONMENT is 0? What does it happen with an INDIVIDUAL_PROFIT of 3000 for all areas and an ENVIRONMENT of 19000?

What can happen if there is only one area with maximum values of individual profit and environment?


To make the model more complete you can ask to turtles to have a complete view of the world, and instead of using a random movement you can find out a way to ask turtles to go in to a specific place.