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view/download model file: population_growth_and_industrial_revolution.nlogo
The model simulates how the population grows, how it settles down in the most favourable lands, favouring the development of industrial districts.
It is inspired by the Malthusian theory of population growth.
Patches represent the lands of the world, while turtles are represented by people who live in this world. People move through the patches looking for grain to eat. They tend to go towards the most favorable lands (green), and they stop once they find a patch which can give them a sufficient amount of resources. When they are on a patch, they cultivate it and they eat the grain produced with their work. Turtles reproduce once they reach a given amount of "energy".
In order to distingush the lands according to the amount of grain they have the model uses different colours:
-green for the most productive lands;
-yellow for the lands with a good amount of grain;
-brown for the lands to be cultivated;
-black for the improductive lands which cannot be cultivated;
-SETUP-PATCHES: this button creates patches with different colour. As explained before, each colour represents a patch with different levels of productivity;
-SETUP-TURTLES: it creates new turtles. Their number depends on the value reported on the slider "initial-number";
-CREATE-LANDSCAPE: this is a button which allows the observer to modify the landscape. After selecting this button, you can draw black lands with the mouse;
-ONE STEP: it runs the model only for one tick;
-GO: this button runs the model forever. Actually the simulation stops after 2500 ticks;
-INDUSTRIAL REVOLUTION: when you select this button, industrial revolution can start in the lands where density-of-population has reached a suitable level for development. It is worthwhile to underline that, even if the the scenary of the industrial revolution is submitted to an obsever's command, the subsequent result is purely endogenous to the model.
Before running the model, set the initial number of agent and the max amount of grain that each patch can contain. You can also choose the age people start working and how many years would they live (which can be thought as a simplified measure of mean life expectancy).
There are two monitors which count the number of turtles and of firms.
There are two plots which show how the population and the firms change versus time.
Starting the simulation you can see how the population grows and expands till the limit of resources represented by the productivity of the patches. You can notice people tendency to concentrate in the most favourable lands. Using the "industrial revolution" button, as explained above, you can also notice the (possible) development of some industrial districts and the different trend of population which follows the industrial revolution.
Very interesting situations may happen by changing '%-patches-with-max-productivity',
'max-age' and 'working-age'. Try to run the model with different combination of these parameters. What happens?
It could be interesting to show how people in a developped society decide to reproduce and what would happen with the introduction of a welfare system (compulsory scholarship, social security, ...).
G. PAVANELLI, Valore distribuzione moneta. Un profilo di storia del pensiero economico, Franco Angeli, Milano, 2003
A. DI VITTORIO, Dall'espansione allo sviluppo. Una storia economica dell'Europa, Giappichelli, Torino, 2005
Wilensky, U. (1997). NetLogo Wolf Sheep Predation model. http://ccl.northwestern.edu/netlogo/models/WolfSheepPredation. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
Wilensky, U. (1998). NetLogo Wealth Distribution model. http://ccl.northwestern.edu/netlogo/models/WealthDistribution. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.