From Wikipedia: "Wonderland is an integrated mathematical model used for studying phenomena in sustainable development. First introduced by (Sanderson 1994), there are now several related versions of the model in use. Wonderland allows economists, policy analysts and environmentalist to study the interactions between the economic, demographic and anthropogenic sectors of an idealized world, thereby enabling them to obtain insights transferable to the real world.
See also this entry in Tom Fiddaman's Model Library.
To explore the behaviour of the model, simply move the sliders for the initial stock value or the parameter value, and the graphs will be updated.
Plot of the 4 stocks against time