Theory of Constraints Handbook - James Cox Iii [20]
Origins of PERT and CPM
The project management literature is intertwined with descriptions of the benefits and problems of PERT and CPM. A brief account is provided illustrating this continuing dialog. PERT and CPM successes immediately caused top management interest. Several researchers provided articles describing the use of these new management tools. Malcolm, Rose-boom, and Clark (1959) provide a status report with a history of the development; examples of the flow plan; the elapsed-time estimates; the organization of the data; the computation of expected times, latest times, slack, and critical path; and probability of project completion by a given date. A description of the pilot application and its full-scale implementation and results to date are provided as well. Almost as soon as this detailed account of PERT appeared, Healy (1961) warned of a problem with the technique, that subdividing activities and their related times can change the project completion date probabilities. Clark (1961) and Millstein (1967) critique Healy’s research based on the realities of managing with PERT, while Roseboom (1961) critiques Healy’s research based on the whether his assumptions are realistic.
Miller (1962) provides a description of how to plan and control with PERT; and Levy, Thompson, and Wiest (1962) provide a similar description of the ABCs of CPM, both in the Harvard Business Review. At the same time, Pocock (1962) describes PERT, its payoff, and problems (PERT is a management responsibility; PERT is no automatic system; PERT often clashes with traditional organization patterns; learning to use a dynamic control system; poor applications; PERT cannot be a rigidly standardized technique). Kelley (1962) provides research supporting the mathematical basis of CPM, and Bildson and Gillespie (1962) provide an extension with a model of PERT (with activity time uncertainty) and CPM (with cost of activity crashing). Paige (1963) provides a detailed description of PERT/Cost. Several research articles followed which examined and attacked the PERT assumptions as being unrealistic or false. The purpose of providing a brief description of the early articles and the articles in the appendices related to various micro (theory) problems being argued even today is to illustrate the types of causes that academic researchers identify for the failures of projects.
Project Failures
In addition to the theory-based research, both anecdotal articles and surveys of different types of project organizations have been taken to determine the level of project failures and causes of failures. In 1957, C. Northcote Parkinson observed that “work expands so as to fill the time available for its completion”—now known as Parkinson’s Law. Others (Marks and Taylor, 1966; Krakowski, 1974; Gutierrez and Kouvelis, 1991) have ascribed the presence of this law to project activities and the results on project duration.
Middleton (1967) surveyed project management organizations in aerospace industries. Respondents provided the following disadvantages of using a project management organization: more complex internal operations (51 percent), inconsistency in application of company policy (32 percent), lower utilization of personnel (13 percent), higher program costs (13 percent), more difficult to manage (13 percent), and lower profit margins (2 percent). Other disadvantages provided were the tendency of functional groups to neglect their jobs, too much shifting of personnel from project to project due to priorities, and duplication of functional skills in the project organization.
Avot states, “The many instances where project management fails overshadow the stories of successful projects” (1970, 36). He identified the major causes of project failure as the following: the basis for the project is not sound; the wrong man is chosen as project manager; company management is unsupportive; tasks are inadequately defined; the project management system