As the figure shows, each additional engineer improves the inspection yield, but the marginal benefit decreases with each addition. Also, when personal yields are more than 70%, the difference in inspection yield between three and four engineers is quite small. This means that if you can maintain personal review yields at around 70% or higher, your team can get very high inspection yields with only two reviewers. Conversely, when personal yields fall to less than about 60%, you should add a third reviewer and possibly even a fourth. In general, the lower the engineers” personal yields, the more reviewers are needed.