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Workforce modelling                         An introduction                             Sally Brailsford                  ...
Aims of today’s session• What is a model?• Brief introduction to System Dynamics modelling• Using System Dynamics to model...
What is a model?
Some myths about modelling•   You need to be a maths wizard to do it•   You need to be a computer geek to do it•   You nee...
System Dynamics• Modelling technique which can be done on paper or  using a computer• Does not always need much data• Syst...
Influence diagrams• As A increases, B also increases        A                            + B• As A increases, B decreases ...
Feedback loops• Negative or balancing loops have an odd number of  “–” signs• Positive or reinforcing loops or vicious cir...
A university example                                                      +                                               ...
A balancing feedback loop                                                      +                                          ...
Behaviour over time   Number of students                        time
A football example                 +       Goals scored per            match                               Money to buy to...
A vicious circle                  +        Goals scored per             match                               Money to buy t...
Behaviour over time   Success of Man United                           time
Negative Feedback Loops• Target seeking (control) loops – try to correct a gap  between target and actual• Stabilising• Ex...
Positive Feedback Loops• Self-reinforcing, unstable, spiral out of control• Examples       • Population / Birth rate      ...
A health example: waiting lists                       Occupancy of                       hospital beds                   +...
Hospital waiting lists                       Occupancy of                       hospital beds                   +         ...
Lessons from this simple model• This is a stable system!• As waiting lists rise, GPs seek alternatives to hospital  admiss...
We need more beds!            + Money for extra     beds                                Political pressure                ...
Unintended consequences             +  Money for extra      beds                                Political pressure        ...
Supply-induced demand• When supply of beds is scarce and waiting lists are long,  demand falls as GPs do not admit patient...
Quantitative SD: stock-flow models• Implemented in computer software• A stock is like a bathtub: water flows into the bath...
Inflow and outflowStock               Tap                                Flow                              Water in       ...
Add more detail …                                    Water in                         DrainageWater tank                  ...
System Dynamics: summary• Powerful methodology for problem structuring:  constructing diagrams is an iterative process, ca...
SD for workforce planning
Add more detail                  Slide 28
A real-life example                      Slide 29
Use of the model•   Used in 2010 for policy-    making by the Sri Lankan    Government•   The Ministry of Higher    Educat...
Exercise• Working in small groups, identify some key factors  which you think will influence the supply of, the  demand fo...
To get you started                                   Third sector                               +    workforce           G...
Recommended reading Business Dynamics: Systems Thinking and Modeling for a Complex World with CD-ROM by John D. Sterman Mc...
Workforce modelling, Sally Brailsford
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Workforce modelling, Sally Brailsford

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Workforce modelling, Sally Brailsford

  1. 1. Workforce modelling An introduction Sally Brailsford School of Management University of Southampton, UKTSRC Workforce day, London 22 September 2011
  2. 2. Aims of today’s session• What is a model?• Brief introduction to System Dynamics modelling• Using System Dynamics to model workforce planning issues• A practical exercise Slide 2
  3. 3. What is a model?
  4. 4. Some myths about modelling• You need to be a maths wizard to do it• You need to be a computer geek to do it• You need expensive software• You need lots of data• It is difficult!
  5. 5. System Dynamics• Modelling technique which can be done on paper or using a computer• Does not always need much data• System structure determines behaviour: i.e. the way that the separate components of any system relate to and affect each other determines the behaviour of the system as a whole• System behaviour may be counterintuitive• Feedback is an important feature
  6. 6. Influence diagrams• As A increases, B also increases A + B• As A increases, B decreases – A B
  7. 7. Feedback loops• Negative or balancing loops have an odd number of “–” signs• Positive or reinforcing loops or vicious circles have an even number of “–” signs• Loops or causal chains show how changes (even quite small) in one part of the system can eventually lead to unexpected changes (possibly quite large) in other parts of the system
  8. 8. A university example + Staff stress levels Students enrolled + - Research papers Student published applications + Reputation of university +
  9. 9. A balancing feedback loop + Staff stress levels Students enrolled + - Research papers Student published applications + Reputation of university +
  10. 10. Behaviour over time Number of students time
  11. 11. A football example + Goals scored per match Money to buy top players + + Man Utd league Gate and TV position receipts + Satisfaction of - Arsenal fans
  12. 12. A vicious circle + Goals scored per match Money to buy top players + + Man Utd league Gate and TV position receipts + Satisfaction of - Arsenal fans
  13. 13. Behaviour over time Success of Man United time
  14. 14. Negative Feedback Loops• Target seeking (control) loops – try to correct a gap between target and actual• Stabilising• Examples - body temperature and sweating
  15. 15. Positive Feedback Loops• Self-reinforcing, unstable, spiral out of control• Examples • Population / Birth rate • Bank balance / Rate of investment
  16. 16. A health example: waiting lists Occupancy of hospital beds + + Referral rates Waiting lists -
  17. 17. Hospital waiting lists Occupancy of hospital beds + + Referral rates Waiting lists -
  18. 18. Lessons from this simple model• This is a stable system!• As waiting lists rise, GPs seek alternatives to hospital admission• Suggests that waiting lists play a useful regulating function by controlling admission rates and keeping bed occupancy down
  19. 19. We need more beds! + Money for extra beds Political pressure + - Occupancy of + hospital beds + + Referral rates Waiting lists -
  20. 20. Unintended consequences + Money for extra beds Political pressure + - Occupancy of + hospital beds + + Referral rates Waiting lists -
  21. 21. Supply-induced demand• When supply of beds is scarce and waiting lists are long, demand falls as GPs do not admit patients to hospital but try other forms of treatment – the effect of the balancing loop• When supply of beds increases, referral rates increase again• Leads to a vicious circle – mitigated of course by the actual increase in beds• Some elements (e.g. bed occupancy) appear in several loops• To determine the actual net effect, we need some numerical data to quantify the model
  22. 22. Quantitative SD: stock-flow models• Implemented in computer software• A stock is like a bathtub: water flows into the bath through the taps and flows out through the plughole• The rate of flow is governed by taps or valves• Material in stocks is continuous, like water - even if we are dealing with individual items like people
  23. 23. Inflow and outflowStock Tap Flow Water in DrainageWater tank bathtub system Outflow through inflow through plughole taps
  24. 24. Add more detail … Water in DrainageWater tank bathtub system Outflow through Natural wastage inflow through plughole taps flow to house Flow into sewage Water Reservoir Sewagetreatment flow after treatment center center outflow treatment Rainfall External source or sink
  25. 25. System Dynamics: summary• Powerful methodology for problem structuring: constructing diagrams is an iterative process, carried out with all the stakeholders• Eliciting opinions from stakeholders and constructing the diagram is a useful exercise in its own right• Can gain helpful qualitative insights into system behaviour even without any data• Software can be used to automate detection of all the feedback loops in more complicated systems• It’s not always necessary to build a quantitative model!
  26. 26. SD for workforce planning
  27. 27. Add more detail Slide 28
  28. 28. A real-life example Slide 29
  29. 29. Use of the model• Used in 2010 for policy- making by the Sri Lankan Government• The Ministry of Higher Education used the model to determine how many university dental school places to fund over the next ten years• The Ministry of Health created 400 additional Government- funded posts over the three years 2012-14 based on the model findings Slide 30
  30. 30. Exercise• Working in small groups, identify some key factors which you think will influence the supply of, the demand for, and the skills base of, workers in the third sector over the next five years• Then construct an influence diagram showing how these are connected• See if you can identify any feedback loops! Slide 31
  31. 31. To get you started Third sector + workforce Government DEMAND funding cuts Ageing population + + Third sector workforce SUPPLY Public sector Private sector job pension cuts availability Third sector workforce SKILLS Slide 32
  32. 32. Recommended reading Business Dynamics: Systems Thinking and Modeling for a Complex World with CD-ROM by John D. Sterman McGraw Hill, 2000 Hardcover £45.59 from Amazon Strategic Modelling and Business Dynamics: A Feedback Systems Approach by John Morecroft John Wiley & Sons, 2007 Paperback £37.04 from Amazon Thinking in Systems: A Primer by Donella H. Meadows Chelsea Green Publishing, Vermont, 2008 Paperback £10.80 from Amazon Slide 33

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