Tragedy of the Commons Systems Archetype

From SystemsWiki

Revision as of 00:38, 15 December 2011 by Phoenix (Talk | contribs)

(diff) ← Older revision | Current revision (diff) | Newer revision → (diff)

A Tragedy of the Commons situation exists whenever two or more activities, each, which in order to produce results, rely on a shared limited resource. Results for these activities continue to develop as long as their use of the limited resource doesn't exceed the resource limit. Once this limit is reached the results produced by each activity are limited to the level at which the resource is replenished. As an example, consider multiple departments with an organization using IT resources, until they've exhausted IT capacity.

Description

Fig. 1 - Tragedy of the Commons Causal Loop Diagram [IM-559]

a activity interacts with resources available to produce a results, R1 at the same time that b activity interacts with resources available to produce b results, R2. a activity and b activity combine to produce total activity which, after some delay, serves to reduce resources available, which constitutes B3 and B4. Everything operates just fine until such time as total activity exceeds the resource limit thereby reducing the resources available to support a results and b results.

Simulation

Fig. 2 is a Stock & Flow diagram equivalent for the above Causal Loop Diagram.

Fig. 2 - Tragedy of the Commons Stock & Flow Diagram

Fig. 2 operates as the description of the Causal Loop Diagram in Fig. 1 though with the addition of a factor and b factor to control the rate of a activity and b activity. Also the resources available provides the limiting factor and is implemented with a replenishment rate to continue to create a level of resources available.

If we simulate the model with the following parameters:

a result = 0.9
b result = 1.0 (just so a and b are slightly different)
resources available = 10
a factor = 0.5
b factor = 0.5 (a factor and b factor don't have to be equal)
replenishment rate = 0 (a fixed resource that doesn't renew)
Time Settings
- Start = 0
- Length = 10
- Step Size = 0.5 (run the insight with 1.0 and see why 0.5 was selected)

It produces the char depicted in Fig. 3. a result and b result depict exponential growth, with b result slightly larger, until they exhaust the resources available. Once resources are exhausted a activity and b activity declines to zero and there are no more results produced.

Fig. 3 - Tragedy of the Commons with no Repenishment Rate [IM-560]

If we now set replenishment rate = 10 and run the simulation again it produces the graph depicted in Fig. 4. Note that because the resources available are being replenished results are produced far longer though eventually resources available becomes equivalent to what's being replenished.

Fig. 4 - Tragedy of the Commons with Repenishment Rate [IM-560]

You are encouraged to alter the values of this model and run the simulation above to get a better sense of the interactions.

Effective Strategies

This structure repeatedly appears in organizational contexts where a service organization supports the success of multiple departments who fail to support the service organization in return. There are two strategies for dealing with this structure, one more effective than the other.

The most effective strategy for dealing with this structure is to wire in feedback paths from A's result and B's result to the resource replenishment so as A and B use resources their results promotes the availability of additional resources.

The alternate, and less effective, strategy for dealing with this structure is to add an additional resource to control the use of resources by A and B. This strategy limits the overall potential results of the structure to the predefined resource limit. It also adds additional resources to the equation, and probably results in endless disputes as to the fairness associated with the allocation of resources. While not really the most appropriate strategy this is the one most often used --- out of ignorance I would suspect.

More ecological approach would be for A and B to realize what they're doing and collaboratively manage their activity and the resource such that it isn't depleted. Yes, it could happen.