Strategic Modelling and Business Dynamics: A Feedback Systems Approach

3.5. Experiments with the Model of Drug-related Crime

3.5.1. A Tour of the Model

Open the file called 'Crime and Drugs' in the CD folder for Chapter 3. An overview diagram like Figure 3.16 appears showing the main sectors, stock accumulations and links.^[] First let's tour the model and note the starting conditions in this imaginary world. Move the cursor into the world of the drug users, to the phrase 'drug-related crime'. This is a good place to begin. A little box pops up containing the number 200, meaning that, when the simulation begins, drug addicts are already committing 200 crimes per month. Move backwards in the causal chain. You will find that addicts collectively need £200 000 per month to fund their addiction (from demand of 500 kilograms per month at a street price of £400 per kilogram) and that each crime yields £1000 on average. Now visit the community and check the 'sensitivity to crime' and 'call for police action'. Typically a crime leads to five complaints, so the call for police action takes a value of 1 000 complaints per month (200 * 5) received from the community.^[]

^[] The reinforcing feedback loop that drives growth in drug-related crime is not visible in the sectorised diagram in Figure 3.16. The reason is that concepts which are the link pins between sectors are duplicated in each of the joined sectors. So, for example, drug seizures appear in the police ...