Tuesday, July 1, 2014

The Flawed Foundation of PERT

By Alexander Laufer and Jeffrey Russell 

One of the most well-known building blocks of project management is the PERT (program evaluation and review technique) method.1 In his comprehensive review of the development of project management, Morris reports:  “Polaris developed a management control procedure [in 1957], PERT; this, together with CPM, was the progenitor of the management systems which over the next 20 years were to become (almost too) synonymous with project management.”2

What evidence was provided about the effectiveness of this scheduling methodology to ensure that it would become almost a household word when discussing project management?  This is how Morris describes the publicity of PERT: “Admiral Raborn and the SPO [Special Projects Office of the U.S. Navy] public relations machinery began publicizing PERT, hailing it as ‘the first management tool of the nuclear and computer age.’  So effective was the publicity that when the first Polaris missile was launched in 1960, press coverage of PERT was almost as great as the coverage of the launch itself.  By 1962, the U.S. Government had issued 139 different documents and reports on the technique.  By 1964, the bibliography on PERT comprised nearly 1000 books and articles…. There is, however, considerable evidence that the method was deliberately oversold, with the aim of keeping Congressional and other external critics at arm’s length.  Raborn used PERT as a tool to control his external environment.”3

One of the sources that Morris used for his analysis was a detailed study of the development of the Polaris system conducted by Harvey Sapolsky.  Here are some of the surprising results of this study, as reported by Sapolsky: “In interviews with contractor executives reviewing their experience with the original PERT system, not one of them said he had used the data generated by that system… Instead, many thought it was the SPO technical officers and engineers who actually had used the PERT system data.  The technical officers and engineers, in turn, denied ever using PERT data… they thought it was the program evaluators… who made use of the PERT system… Persons who held positions in Plans and Programs, however,… never used the system; rather they thought that it was… the plant representatives who worked with the PERT reports.  The plant representatives were similar in their response: ‘No, it must have been someone else.’” 4

Sapolsky concludes by “putting the myth in perspective”:  “An alchemous combination of whirling computers, brightly colored charts, and fast talking public relations officers gave the Special Projects Office a truly effective management system.  It mattered not whether the parts of the system functioned or even existed.  It mattered only that certain people for a certain period of time believed that they did…. The Special Projects Office won the battles for funds and priority.  Its program was protected from the bureaucratic interferences of the comptrollers and the auditors.”5 Polaris was a success, but what really stood behind its success?  Davies and Hobday highlight the real practices that contributed to the Polaris’s success: “PERT was not actually used to build the system…. Instead Polaris’s success was the result of inspired leadership, good management and a shared spirit of commitment… PERT… was a deeply flawed management tool…. used primarily to impress visitors… and to build up a myth of management effectiveness. ”6

Stout addresses the wider and long-lasting implications of disseminating the myth, the rational method, while at the same time ignoring the real soft practices that led to Polaris’s success: “What is retained is not an understanding of the actual practices, but the magic and symbolism of ‘the system.’… The assumed effectiveness of PERT was not based on an evaluation of its role in Polaris; rather it was a matter of inference.  The inference took the symbolic form: Polaris was a success; PERT was used; therefore, PERT was at least partially responsible for the success.  Even if the second claim was true, and it is not, the inference is still questionable.  But it is on this that PERT has achieved its popularity.”7

Our questions:

  • To what extent do you think that the quick popularization of PERT can be attributed also to the prevailing assumption that one can (and should) impose “geometric order” even early in the life of the project?
  • Are you sure that the current popular project management methods and tools are supported by better evidence than the ones that were used to support the effectiveness of the PERT method?8

       1.      This blog is an excerpt from: A. Laufer, Breaking the Code of Project Management, New York, NY: Palgrave, 2009, 5-6. 

2.      P.W.G. Morris. 1994. The Management of Projects. London, UK: Thomas Telford Services, 25.  Program Evaluation and Review Technique (PERT) is an event-oriented network analysis technique used to estimate program duration when there is uncertainty in the individual duration estimates. Critical Path Method (CPM) is a network analysis technique used to predict project duration by analyzing which sequence of activities (which path) has the least amount of scheduling flexibility.  

3.      P.W.G. Morris. 1994. The Management of Projects. London, UK: Thomas Telford Services, 30-1.

4.      H.M. Sapolsky. 1972. The Polaris System Development. Cambridge, MA: Harvard University Press, 123-24.

5.      H.M. Sapolsky. 1972. The Polaris System Development. Cambridge, MA: Harvard University Press, 129.

6.      A. Davies and M. Hobday. 2005. The Business of Projects: Managing Innovation in Complex Products and Systems. Cambridge, UK: Cambridge University Press, 151-52.

7.      R. Stout Jr. 1980. Management or Control?: The Organizational Challenge. Bloomington, IN: Indiana University Press, 25-6. 

8.     An article on the same subject, stressing the need for more elaborate case studies like Sapolsky’s research, was published in 2012 by M. Engwall:  PERT, Polaris, and the realities of project execution. International Journal of Managing Projects in Business 5.4, 595-616.