Notes
Outline
Urban Dynamics in Trenton
Subsidized Housing Push is Bad for Trenton (1 of 3)
Summer start is hoped for homes
Article discusses a new subsidized housing project.
http://www.nj.com/mercer/times/index.ssf?/mercer/times/02-12-IVQR1EVB.html
(appeared in 2/12/02 Trenton Times)
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Dan’s response:
Building homes for low income people sounds like a good idea.  But if it were such a great idea, why aren't our wealthy suburban neighbors doing it instead of paying us to do it for them?
Turns out that while it is certainly a good thing for people to have comfortable homes and housing construction is a short term employment boost, the long term effects of subsidized housing are what keep communities like Trenton in the hole.
It's difficult to do, but if you explore the effects of  subsidized housing in the "long term" it has several "unintended" effects, this according to the folks who model city dynamics.
1) Low cost housing increases the number of low income people that move to a city
2) Low income people use a disproportionate amount of city services (schools, police, health)
3) Housing subsidies and increased city services lead to higher tax rates which discourage other new development
Subsidized Housing Push is Bad (2 of 3)
The bottom line is that making Trenton more attractive for low income people, makes it a Mecca for emigration by the poor.  We should be more worried about creating a better community for the folks who already live here.  The way to do that is by attracting industry.
But even so, do we really have an unemployment problem in Trenton?  What is almost certain is that it will be worse as we attract more low income people to compete for jobs that do exist and nobody ever complained about too many jobs.   Also, Trenton has limited space and by crowding out industry, office development and higher end housing, we block economic recovery.
Understanding all of these effects and exactly how they interact is hard to do.  The science of doing this is called "system dynamics" and when applied to cities is called "urban dynamics".  It was originally developed by Dr. Jay Forrester at MIT and later embellished by Dr. Alan Graham also from MIT and a colleague of mine.
The basic idea is that cities are complex systems of causes and effects whose relationships can be represented by mathematical models.  Businesses use these models to guide their strategies.  The models include feedback loops that show systems to reach an equilibrium over time.  The question is, what variables can we affect (e.g. spending on housing, crime, marketing) and what are the ripple effects over time?  Urban dynamics models that have been built show spending on subsidized housing to be one of the main culprits in a city's continued downward spiral to a low level of equilibrium (as defined by mean income).
Do we in Trenton really want to risk this?
Subsidized Housing Push is Bad (3 of 3)
A model that predicts outcomes in a city like Trenton is necessarily complex and expensive to build and maintain.  However, we need not build a model in order to consider and debate the dynamic aspects of our city's policy decisions. In all fairness to our politicians and press, it is difficult to consider long term effects especially when they have short term negative consequences like a shortage of housing.  But part of breaking the cycle is upgrading our knowledge of how the city behaves.
I know I sound like I'm preaching and teaching but I know that everybody on my "To:" list is concerned about Trenton's economic recovery and wants to help break the cycle that it has apparently been in for many years.  I'm attempting to put some new thinking into the mix of public debate and hope that you will all see it in that light.
Additionally, the system models might be wrong.  But only through a better understanding of the system can we make informed policy decisions.   I'll be interested in the feedback,  including the "darts".  Also if you'd like more info on what an urban dynamics model looks like, let me know.
Trenton is "Downtown Mercer County"
"An Illustrative Example of an..."
An Illustrative Example of an Urban Dynamics Model
The following model is a diagrammatic view of a simple dynamic model.  It looks complicated even though I've left a lot of things out in the interest of space (schools, crime and marketing to mention a few).  The green arrows are "increases" the red arrows are "decreases".  The fat arrows are major relationships.  The boxes are "levels" (i.e. numbers of things), the arrow boxes are flows (changes in levels) and the circles are variables.  All of the symbols contain mathematical relationships.  Also there would normally be delays built into a model like this (i.e. the presence of new housing doesn't immediately attract new residents).
From this model you should be able to see that every action has a reaction and that modeling a city is complicated.  Furthermore, because it is complicated oversimplified “cause and effect” thinking should be avoided.
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