Part Three - Model Alterations
Structural Changes in Urban Dynamics: Housing Obsolescence and Housing Demand by Nathaniel J. Mass
This explores a reformulation of the rate of housing-obsolescence saying that it should be slowed by an excess of housing in the next lower category of housing quality. However, after running some simulations, Mass shows that the result is the same.
Modeling City-Suburb Interactions by Alan K. Graham
The urban dynamics model assumes that people live and work in the same city, not accounting for commuting. The conclusion is that the additions to the model do not impact the recommendations.
Two Modifications to the Tax Sector of Urban Dynamics by Michael R. Goodman
Forrester's urban dynamics model applied outside funding to new programs in a city. One modification could be that outside funding would only go towards paying down the debt, "a revised financial aid subsidy program." This does result in an improvement in the Tax per capita radio, Tax ratio needed, and the Underemployed to labor net.
Another modification could be to change the tax needs per person such that they "increase with progressively higher local unemployment rates, and conversely." However, there is no difference in the results after this is implemented partly because this is already incorporated into the old model although not explicitly.
A Dynamic Model of Land Pricing and Urban Land Allocation by Nathaniel J. Mass
The Urban Land Market is incorporated into the Urban Dynamics model. This also did not have a significant impact on the results. However, this analysis can help city planners with determining appropriate zoning policy. "Zoning policy would need to be combined with other policy measures designed to control urban population."
Adapting Urban Dynamics to Lowell by Walter W. Schroeder III and John E. Strongman
Here is some analysis about whether the urban dynamics model accurately describes Lowell, Massachusetts. They conclude that it can, and that it can help design policy for urban renewal.