Not that long ago, a friend of mine, who is a project manager for a large company, was complaining about never being able to complete a project for his organization, since he is more than often transferred from one project to another, depending on priority changes. Recently, another acquaintance of mine was wondering about how to evaluate the impact of team changes on the project proceedings. According to her, such changes involve significant consequences, but she does not know how to evaluate them.
Companies are said to be more agile and they wish to be able to regularly change priorities. Those changes bear consequences, everyone knows it, but how can we evaluate them?
A simple method was created to answer that question: CoCoMo (Constructive Cost Model). There is a model which enables to estimate the effort of a software project depending on several parameters. That model was conceived by Barry Boehm and his team, and it keeps evolving at USC, the University of South California. The calibration has been done on a large number of projects.
The equation of CoCoMo is as follows:
Coefficient b is close to 1 and gathers influent factors in relation with the organization’s maturity.
Coefficient a gathers influent factors in relation with the product, the platform, the project and the team. Amongst the factors that are related to the team, there is “PCON”, that stands for Personnel Continuity. The PCON parameter is a multiplication factor of the effort that varies from 0.81 to 1.29 depending on the stability of the team.
- The lowest is a turnover of 3%: the team hardly ever undergoes changes.
- The highest is a turnover of 48%: half of the team is renewed each year. In that particular case, the cost of the project will be 59% higher than with a highly stable team.
Thus, we can deduce the impact of the turnover on the effort of the project.
So, if half the team changes each year, the project will cost close to 60% more than with a team that remains unchanged, with equal competences.
But let’s imagine that the staff is being replaced by less qualified employees, and without as much experience with the application, the impact would then be as follows:
On initial examination, we can consider that the additional charge (in %) of the project is two to three times the turnover (in %).
Here, neither the impact of a temporary stoppage of the project, nor the impact on the delivery date are evaluated. We realize that the lack of stability of the team can have disastrous consequences on the project cost.
Those data are given by way of indication, since they can vary from one context to another, but they give an order of magnitude. We are now aware that agility has a cost, but it might be better sometimes to wait a few months to eventually cut expenses and deliver faster.
