Re: When are SD models appropriate?

Stephen Robbins (
Sat, 17 Dec 1994 15:29:44 EST5EDT

> To:
> From: (Joe Kilbride)
> Subject: Re: When are SD models appropriate?

> I am referring to a computer model of system structure using stocks, flows,
> feedback loops.
> Or do we just create SD models because *we want to* and have found
> we could talk into it? There has to be more to it than that...

Having just completed MIT's course in system dynamics, my impression
is that system dynamic models are appropriate whenever you have
multiple feedback loops in a system, and/or long delays between cause
and effect. What the models helped me understand most in the course
of the semester was the overall behavior patterns of systems. For
example, we built a model of a particular marketplace, and discovered
that, given the model's assumption, there were certain policies a
company could follow to guarantee a profit in that marketplace under
a wide variety of circumstances. [It also showed us that the market
had a prisoner's dilemma characteristic--we could win BIG if we
followed an aggressive strategy and our competitors played it more
mildly. But by playing it mildly, we capped our upside, but could
make SOME profit in every scenario. If both players were aggressive,
the market tanked.]

- Stever

Stever Robbins
Accept no substitutes! PGP key available upon request
"You're only young once, but you can be immature forever."