22 July 2009 3:00 PM
One of the persistent themes of urban change is the presence of positive and negative feedback loops. Crime provides an excellent example. An increase in crime stretches police resources, decreasing the odds that any individual crime is solved and thereby increasing the return to crime -- and generating more of it. Which further stretches police resources.
This process touches off other feedback loops. Rising crime reduces property values which reduces property tax revenue. This limits city resources and further strains the police force and the public services which might otherwise keep at risk residents from turning to crime. Declines in public safety and service quality encourage mobile residents to leave, and since richer residents are more mobile that has a strong negative impact on the revenue base, further complicating matters.
Out-migration also reduces property prices which then attracts people who need cheap housing, which will tend to be economically distressed individuals and households. These families then demand more city services while contributing less to public coffers, and so on.
Luckily, he says, there are positive feedback loops too.