The model for this simulation was created using iThink Systems Thinking software from isee systems. For more information about iThink or to download a free trial version, visit

Click on the link below to download a zipped archive of the original iThink (.itm or .itmx) model file. After downloading and unzipping the archive, you can open, view and run the model on your computer using iThink or the free isee Player software. If you copy any part of the model, you must give credit to the author and license it under the Creative Commons Attribution-Share Alike 3.0 license.

Download Model (Zipped Archive)