There are several different versions of the model which you can reach by following the link at the bottom of the page. The simplest one (which is not the HN lin

There are several different versions of the model which you can reach by following the link at the bottom of the page. The simplest one (which is not the HN link) is purely random. The more sophisticated models add other factors like investments. In the most complex model, the inequality is very dramatic indeed.