Critical Chain Project Management

Why Projects Fail to Deliver on Time

In 1997 Eliyahu Goldratt attempted to come up with an answer to the perennial problem – why do so many projects deliver late? His response was the critical chain approach to project management. In this series of blogs I’m going to give you my take on the method starting with Goldratt’s ideas on why projects deliver late.

When we give estimates we often secretly add some padding to the figure. This is our safety margin, because we all confuse the word estimate with commitment. Now you might think that in many cases this safety margin isn’t needed, so quite a number of tasks would deliver early. Goldratt observed this rarely happened. Most tasks deliver late – over and above the safety margin. Why was that? Goldratt put forward a number of reasons:

Parkinson’s Law. Cyril Northcote Parkinson noted in a humorous Economist essay way back in 1955 that, “Work expands so as to fill time available for its completion”
Murphy’s Law – anything that can go wrong will go wrong.
Student Syndrome, many people wait till the last possible moment to start a task, wasting any buffer built into the original estimate.
People don’t like delivering early; managers might come to expect it!
If the next part of the project will not be ready, why deliver before they can start?
Often in multi-project environments, in the push to show progress, many projects are started simultaneously. Resources then have to multi-task between projects. The Costs of Multitasking slide below shows why this causes delays. The top line shows a resource completing work on project A, then project B and lastly project C – time runs across the horizontal. Compare this with the bottom line where work in the projects is interleaved. Work on projects A & B is now delivered later with no loss or gain to project C.
When we multitask it takes some time to get our minds back into an old task, i.e. there is a hidden switch duration.

Costs of Multi-tasking

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In part 2 of this series I will look at the basics of the critical chain approach and why they help to decrease the impact of these problems.

Are there any other reasons you think project deliver late – interested to hear your comments below.