The Staffing Effect

Roscoe grabbed his pencil. "Let's superimpose a staffing profile on the previous curves. Waterfall projects staff up early, whereas iterative projects defer staffing, relatively speaking. Small, elite teams that can go fast are best for doing most of the work in the early phases, in other words, for the Inception and Elaboration iterations.^[7] Then, you add significant numbers of people as you move into iterations for the later phases, Construction and Transition. The difference looks something like this..." as he drew some new curves to produce Figure 5.4.

^[7] Standard practice is to divide the project into four phases: Inception, Elaboration, Construction, and Transition. Each phase has one or more iterations. We'll return to this in Chapter 12.

Figure 5.4. Roscoe's third drawing, amendedwaterfall versus iterative, with staffing.

"Now, let's consider a project that gets canceled at point D on each curve. The resources that will be consumed to that point are indicated by the shaded areas on the curvesthe area under the staffing curve from the start to point D, when cancellation occurs." His shaded additions are shown in Figure 5.5.

Figure 5.5. Roscoe's third drawing, further amendedwaterfall versus iterative, with staffing shaded.

"Compare the shaded areas. The iterative scenario is superior for two reasons: You decide to abort earlier, and you have much less invested because you started small and planned to staff up later."

Roscoe was right, but there is one small detail I should mention here. Although iterative development uses far fewer people early in the project than waterfall, in general those people are more experienced and therefore more costly. So the shaded areas reflect manpower loading, but not necessarily actual staffing costs. This is often a second-order effect, however, simply because of the huge differences in number of people employed.

Roscoe continued. "The implication here is that you can launch more iterative development projects, because you can cut them off early with relatively small losses. This benefit is undercut somewhat because of the limited number of really good people within most organizations who can be deployed on early iteration work. These people are always in short supply."

Roscoe was coming in for his landing. "Remember, too, that waterfall is a disaster, because as staffing costs growthe shaded areait becomes organizationally and politically harder and harder to cancel the project. When you cancel an iterative development project early, you have a relatively small number of people to redeploy. When you cancel a large waterfall project late in the cycle, it dislocates a large number of people."

I saw his point. In the end, if you have to cancel a project for any reason, it just makes good business sense to cancel it early, before you have too much in the way of sunk costs. And the staffing approach for iterative development keeps these costs to a minimum in the early phases.