Productivity of Software Enhancement Projects: an Empirical Study

Background. Having a correct, although approximate, knowledge of software development productivity is clearly important. In some environments, the belief that software enhancement projects are characterized by higher productivity than new software development has emerged. Aim. We want to understand whether the mentioned belief is rooted on solid bases or is due to some cognitive biases. Method. An empirical study was performed, analyzing the data from a large dataset that collects data from real-life projects. Several statistical methods were used to evaluate the unitary cost (i.e., the cost per Function Point) of enhancement projects and new developments. Results. Our analyses show that–contrary to some popular beliefs–software enhancement costs more than new software development, at least for projects greater than 300 Function Points. Conclusions. Project managers and other stakeholders interested in the actual cost of software should reject ill-based evaluations that the productivity of software enhancement is greater than new software development. More generally, objective evaluations based on the analysis of representative data should be preferred to evaluations affected by cognitive biases.