27.4. Effect of Project Size on Productivity

Productivity has a lot in common with software quality when it comes to project size. At small sizes (2000 lines of code or smaller), the single biggest influence on productivity is the skill of the individual programmer (Jones 1998). As project size increases, team size and organization become greater influences on productivity.

How big does a project need to be before team size begins to affect productivity? In "Prototyping Versus Specifying: a Multiproject Experiment," Boehm, Gray, and Seewaldt reported that smaller teams completed their projects with 39 percent higher productivity than larger teams. The size of the teams? Two people for the small projects and three for the large (1984). Table 27-2 gives the inside scoop on the general relationship between project size and productivity.

Table 27-2. Project Size and Productivity

Project Size (in Lines of Code)	Lines of Code per Staff-Year (Cocomo II Nominal in Parentheses)
1K	2,500 25,000 (4,000)
10K	2,000 25,000 (3,200)
100K	1,000 20,000 (2,600)
1,000K	700 10,000 (2,000)
10,000K	300 5,000 (1,600)
Source: Derived from data in Measures for Excellence (Putnam and Meyers 1992), Industrial Strength Software (Putnam and Meyers 1997), Software Cost Estimation with Cocomo II (Boehm et al. 2000), and "Software Development Worldwide: The State of the Practice" (Cusumano et al. 2003).

Productivity is substantially determined by the kind of software you're working on, personnel quality, programming language, methodology, product complexity, programming environment, tool support, how "lines of code" are counted, how nonprogrammer support effort is factored into the "lines of code per staff-year" figure, and many other factors, so the specific figures in Table 27-2 vary dramatically.

Realize, however, that the general trend the numbers show is significant. Productivity on small projects can be 2 3 times as high as productivity on large projects, and productivity can vary by a factor of 5 10 from the smallest projects to the largest.