As a rough rule, three programmers organized into a team can do only twice the work of a single programmer of the same ability—because of time spent on coordination problems. Moreover, three groups of three programmers can do only twice the work of a single group—or four times the work of a single programmer—for the same reason. Thus, an eight-month project for a single programmer might be done in four months if we are willing to put three people to work on it or in two months if we are willing to allocate nine.
one "data point": triple the # of engineers, only double the throughput on shared project.
