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EXPLORING GOLDRATT’S CRITICAL CHAIN 85

time estimates, while a common practice, is not a good thing.
There are better ways to allow for the uncertainty that exists
in all projects.

Exploring Goldratt’s Critical Chain Theory

Of all the emerging solutions for shared contingency, the one gaining the most at-
tention is one presented in a very interesting book by Eliyahu Goldratt, called Crit-
ical Chain (North River Press, 1997). Eli Goldratt has been successful in using the
fiction novel method to promote his hypothesis on the Theory of Constraints, via
the subject book and two others: The Goal (1992), and It’s Not Luck (1994).

There have been a plethora of papers, both in print and on websites, either ex-
tolling the benefits of the critical chain approach, or advising restraint in adopting
this theory. The discussion tendered herein is entirely neutral, finding both praise
and fault with aspects of theory and practice of Critical Chain Project Manage-
ment (CCPM), as presented by Goldratt and supporting disciples.

As I shared my thoughts with two colleagues (both involved in developing soft-
ware for project management), the question arose as to whether there were two
separate camps. One said that you had to be a supporter of either CCPM or tradi-
tional CPM (TCPM), but couldn’t straddle both philosophies. I choose to disagree.
I am not ready to either abandon TCPM or adopt CCPM lock, stock, and barrel.

For example, looking at just one of the beliefs associated with the two camps,
let’s consider the rules for multitasking. In TCPM, it has become the accepted
practice to assume that resources will, at times, move back and forth between
concurrently scheduled tasks. In fact, we often find that such movement pro-
duces more efficient schedules and utilization of resources, and we have criti-
cized software that does not support resource assignment splitting. Now Goldratt
comes along to dispute that assumption. He says that multitasking is required
only because we establish task durations that are longer than the actual time re-
quired to perform the tasks. He claims that multitasking is inherently inefficient.
If we reduce the estimated task duration to match the real effort, says Goldratt,
then we don’t have to shift the resources. CCPM, therefore, deliberately disal-
lows resource assignment splitting, claiming that it is a negative attribute rather
than a preferred capability.

In brief, Goldratt’s position is that project schedules are always too long due
to the safety factors that are added to the task estimates. He claims that esti-
mates are usually based on a 90 percent confidence factor (rather than 50%). In
addition task durations are also padded unless the performer is assured that
everything needed to do the task will be ready at the start of the task (which is