"The first step in modeling is to re-create the problem." Jay Forrester

Stage 1. When modeling a dynamic process--one that plays out over time--it is useful to divide the work into successive stages that contribute to the overall purpose of the modeling effort.  If that overall purpose is to improve performance, it is tempting to jump right into the policy modeling mode and ‘weigh the options’ for change.  However, as suggested above by Forrester, policy design is likely to fail without understanding historical problematic performance.  That’s why the first stage of building a useful model is the explanatory stage.  Explanatory modeling identifies the systemic reasons for a pattern of historical behavior viewed as a serious issue (e.g., rising pollution levels, falling profits, or stagnant economic growth). A useful explanatory model re-creates the problematic behavior pattern on the computer screen by accurately structuring the historically significant causal factors.

It's not enough to know where we are.  We must know how we got here and where we're headed.  That's the purpose of an explanatory model.

                                              Policy Model          Implementation Model

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"We cannot solve our problems with the same thinking we used when we created them." Albert Einstein

Stage 2.  Policy modeling explores and evaluates ways to prevent continuation of undesirable trends.  A policy model is more likely to be useful when combined with a good explanatory model that reveals the structural causes of the problem.  Better performance in the future requires re-structuring historically problematic causal factors in ways that promise cost-effective change in the real-world system that the model describes.  Above, Einstein challenges us to think differently about how things could be done.  Recognizing good alternatives requires knowing how things were done in the past.  As Forrester says, “Only by clearly understanding what is causing the problem can one begin to see where policy attention should be focused."  

If an explanatory model shows that we are on the wrong path,
a useful policy model helps us envisionpromising new directions.

 Explanatory Model                                          Implementation Model

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"I'm a policy man.  I let others worry about implementation." Will Rogers

Stage 3. During World War I, humorist Will Rogers underscored the need to combine implementation planning with policy design when he quipped that the best defense against enemy submarines was ‘boiling the Atlantic Ocean.’ A policy model is unlikely to be useful if it merely reflects wishful thinking about solutions to a problem.  implementation modeling modifies the stage-two policy model by adding structure that reflects 'operational thinking' instead of ‘wishful thinking.'  Operational structure shows key steps in the change process and enables assessment of their feasibility as well as cost-effectiveness.

There are limits, however, to quantitative implementation modeling.
At some point, we should stop modeling but keep talking. A useful model adds value to policy discussions that take place anyway.


To learn more about the three-stage modeling process
and see some examples, download this paper.

 Explanatory Model          Policy Model                                                   

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