system dynamics douglas m. stewart, ph.d. anderson schools of management university of new mexico...
TRANSCRIPT
System Dynamics
Douglas M. Stewart, Ph.D.
Anderson Schools of Management
University of New Mexico
Adapted from Senge, P. The Fifth Discipline, Doubleday/Currency, 1990.
Why System Dynamics
TQM requires a systems view of the world A new paradigm required See the interrelationships rather than the
linear cause-effect chains See the process of change rather than a
snapshot In systems thinking every influence is both a
cause and effect
Introduction to Systems Diagrams
From any element in a situation you can trace arrows that represent the influence on another element.
Example: Filling a glass of water
Faucet Position
Water Flow
Current Water Level
Perceived Gap
Desired Water Level
Am I filling the glass of water?
Or is the level of water controlling my hand?
Building Blocks of Systems Thinking
Reinforcing Loops (Positive Feedback) Balancing Loops (Negative Feedback) Delays
Reinforcing Loops
Sales
Satisfied Customers
Positive Word of Mouth
If the product is good we have a virtuous cycle.
If the product is bad we have a vicious cycle.
Reinforcing Loops
The snowball effect Accelerating growth or accelerating decline These systems can take you by surprise!
Balancing Loops
Body Temperature
Desired Body Temperature
Temperature Gap
Adjust Clothing
Balancing Loops
System reverts to status quo Often in business the goals are implicit When there is resistance to change, look for
a hidden balancing process
Delays: The Sluggish Shower
Current Water Temperature
Temperature Gap
Shower Tap Setting
Desired Water Temperature
Delays
When you tell the story add the word “eventually”
Cause the system to overshoot the target Aggressive action produces the opposite of
what is intended
An Example: Reducing Burnout
Actual Hours Worked
Heroism GapThreat of being perceived as uncommitted
Implicit goal of 70 hour workweek
Archetype 1: Limits to Growth
A reinforcing process is begun to produce a desired result. It works, but also creates unintended side-effect (a balancing process) that eventually slows down success.
Limits to Growth
Growth
Promotion Opportunities
Morale
Motivation and Productivity
Saturation of Market Niche
Size of Market Niche
Where is the leverage?
Limits to Growth
The tendency is to push hard The leverage not in the reinforcing loop, but
removing the limits on the balancing loop
Don’t push growth. Remove the factors that limit growth
Archetype 2: Shifting the Burden
An underlying problem generates symptoms that demand attention.
But…underlying problem is obscure or costly to confront.
So… people shift the burden to other solutions that address the symptoms.
Shifting the Burden
Personnel Performance Problems
Bring in HR Expert
Develop Managers’ Abilities
Expectations that HR Experts will solve problem
Shifting the Burden
Beware the symptomatic solution Benefits are short term at best Pressure on symptomatic response only gets
larger
Archetype 3: Eroding Goals
A shifting the burden type structure where the short term solution is letting the long term goal decline.
Customers are dissatisfied with late schedules. Production scheduling never really under control. Company says we ship to schedule 90% of time. But…every time the schedule begins to slip, they add to quoted delivery times.
Eroding the Goals
Gap
ConditionActions to
Improve Conditions
Pressures toAdjust GoalGoal
Early warning symptom:“It’s OK if our performance standards slide just a little until the crisis is over”
Principle: Hold the vision
Archetype 4: Success to the Successful
Two activities compete for limited resources. The more successful one becomes, the more support it gains, thereby starving the other.
Manager has two protégés. One gets sick for a week, the other gets preferential treatment. The first feeling approval flourishes and therefore gets more opportunity. The second, feeling insecure, languishes and eventually leaves.
Success to the Successful
Allocation to A instead of B
Resourcesto B
Success of B
Resources to A
Success of A
Warning symptom: One of two interrelated activities is beginning to do very well and the other is struggling
Principle: Look for overarching goal to balance both, or decouple the shared resource.
Tragedy of the Commons
Individuals use a joint resource on the basis of individual need. At first they are rewarded for using it. Eventually they get diminished returns, which causes them to intensify their efforts. The resource becomes depleted.
Several divisions use a common retail sales force. Each is concerned that sales force will not give enough attention to their products. One manager sets higher than needed targets. Other managers followed. Sales force becomes tremendously overburdened, performance declines and turnover increases.
Tragedy of the Commons
TotalActivity
Individual B’sActivity
Net GainsFor B
Individual A’sActivity
Net GainsFor A Resource
Limit
Gain perIndividualActivity
Warning Symptom: There used to be plenty for everyone. Now things are tough. I will have to work harder to succeed.
Principle: Manage the commons through education and self-regulation or an official regulation
Archetype 5: Growth and Underinvestment
Growth approaches a limit which can be pushed out with investment in additional capacity. But if investment is not aggressive enough to forestall growth, it may never get made.
People express was unable to build service capacity to keep up with demand. Firm tried to outgrow problems. Deteriorating service quality, increased competition and lower morale followed. Firm relied on underinvestment strategy until customers no longer wanted to fly airline.
Growth and Underinvestment
Number ofPassengers
IncreasedFlights
Revenues
Reputation
ServiceQuality
Perceived needTo improve quality
Additions toService Capacity
ServiceCapacity
QualityStandard
Warning: We used to be best and will be again, but right now we need to conserve resources and not overinvest
Principle: Build in advance of demand as strategy for developing it. Hold the vision on quality standards.
Spend on R&D to Drive Growth
Revenues
R&D Budget
New Products
Size of Engineering Staff
Management Complexity
Management Burden to Senior Engineers
Product Development
Time Senior Engineers Ability to Manage
The growth of survey based business research.
Total #Surveys
Researcher B’sSurveys
Net ResearchFor B
Researcher A’sSurveys
Net ResearchFor A Business Survey
Tolerance
Survey Burnout andResistance