Many Scrum teams have found that excessive overtime reduces productivity. The frequent inspection of work done on a daily basis makes measuring productivity far easier with Scrum. One of the reasons for this is that a Scrum team can adapt their practices and see what effect those changes have on their effectiveness.
Jeff Sutherland reports that one of the companies he coaches has measured the productivity of teams using Scrum and waterfall-like practices under different overtime conditions. They produced a graph they call the Maxwell curve:
This is hardly a scientific study (e.g. I'm real curious about how they measure story point velocity in a waterfall environment) but it is a very strong visual argument for what is intuitive about how people work:
- Teams of people who take ownership of their work and make a commitment are more productive, but this high level of productivity cannot be sustained for 60 hours a week.
- When people are treated like cogs in a machine (handed estimated tasks that have to be completed to a predetermined schedule), they can indeed produce more at 60 hours a week that 40. However the productivity of cog teams is not nearly as high as committed teams because their intensity is not nearly at the same level.
Think of a runner sprinting and a jogger. The sprinter will be faster, but cannot maintain that pace as long as the jogger.
The question is "who covers the greater distance?". Does the team that "jogs" go farther in 60 hours than the team that "sprints" for 40? Maybe, but which is sustainable? Which team would you rather be on? Also, is it the same progress? Consider Jeff's comment on overtime with waterfall:
Overtime doesn't work in waterfall. It introduces technical debt. It works short term for the project leader as long as no one discovers he is damaging the code base. Velocity gets slower and slower with overtime but it may be years before management realizes they have to pay for the technical debt. By then the project leader has been promoted.