REPLY Age of material in a stock (SD6430)

[SDMAIL George Richardson]

Posted by  George Richardson <gpr at albany.edu>


>On Apr 20, 2007, at 5:33 AM, SDMAIL Jay W. Forrester wrote:
> Can someone supply some examples of where the way of computing
> age in a stock will alter the direction of policy
> recommendations to improve the behavior of a system?


Great question.  We have at least one really good example:  Being  
able to keep track of the average lengths of stay in stocks was  
crucial to all of our modeling efforts to help NYS counties cope with  
welfare reform (see Using Simulation Models to Address 'What If'  
Questions About Welfare Reform. A.A. Zagonel, J. Rohrbaugh, G.P.  
Richardson, and D.F. Andersen. Journal of Policy Analysis and  
Management 23,4 (2004): 889-920).

The reform legislation, passed by the Republican-dominated Congress  
and signed by Clinton, removed the Federal guarantee of (potentially)  
lifetime support for people on welfare.  The legislation replaced  
that lifetime guarantee, in place since the depths of the Depression,  
with Temporary Assistance to Needy Families (TANF).

An individual is now eligible for up to five years (cumulative in  
one's lifetime) of TANF support from the Federal government.  
Once a  person uses up that five years in various spells of poverty, 
they are  on their own, or depend on support from states and counties.

Our model-based efforts with three New York State counties was  
designed to help counties anticipate the system dynamics and cope  
with the added strains on their resources once people would begin  
timing out of TANF.  To do it formally, we had to keep track of the  
years people accumulated in the various stocks in the client-flow  
system.   There were six stocks tracking the various ways clients  
flowed through the system, and hence a pretty complicated six-stock  
coflow system to keep track of the average cumulative lengths of stay  
on TANF.

George P. Richardson
Chair of public administration and policy
Rockefeller College of Public Affairs and Policy
University at Albany - SUNY, Albany, NY 12222 
Posted by  George Richardson <gpr at albany.edu>
posting date  Sat, 21 Apr 2007 21:44:12 -0400