Motivation: Reduce the Risk of Losing a Key Person

With pair programming, the risk of losing key programmers is reduced because multiple people are familiar with each part of the system. If a pair works together consistently, two people are familiar with a particular area of the program. If the pairs rotate, many people can be familiar with each part. A common informal metric (invented by Jim Coplien of AT&T Bell Labs) is referred to as the "truck number." "How many or few people would have to be hit by a truck (or quit) before the project is incapacitated?" The worst answer is "one." Having knowledge dispersed across the team increases the truck number and project safety.

As programmers rotate among the group, they get the chance to know many on their team more personally. This familiarity breaks down many communication barriers. Team members find each other much more approachable. They struggle with questions or lack of information for less time before getting out of their chair and going to ask the right person a question because they know that person quite well. Pair rotation enables person-to-person sharing of tacit knowledge, ideas, and insights that are not documented and are hard to articulate. Through pair programming, sharing of tacit knowledge takes place in the normal course of the programmers' day; no special resources, systems, or repositories need be allocated for this important knowledge sharing. Pair programming provides an organizationally supported vehicle for continual, ongoing conversations between programmers. Through these conversations, knowledge management takes place, along with a corresponding decrease in the risk of losing a key person on the team.