"Adding manpower to a late software project makes it later." If a software project is delayed, one or the other may tend to make up some of the delay by putting more people on the team. However, this irgnores the fact that new employees first need a ramp-up phase before they can start working productively. The more complex and extensive the development project, the longer that ramp-up phase. During this ramp-up phase, existing employees lose productivity because they spend time on onboarding the new team members.