Jason and Felipe Engineer discuss Brooks's law from software development. Brooks worked at IBM, found on thousands of projects that adding more people or spending overtime when behind schedule doesn't make projects finish earlier, data doesn't support it. Short-term overtime (less than 2 weeks) can make gains, but long sustained overtime or adding manpower up and down is detrimental. Why adding people doesn't help: communication channels increase exponentially using formula n(n-1)/2—two people have one channel, three people have three channels, ten people have 45 channels, 200 people on $20M job have 19,900 channels. Context switching: if interrupted while at 100% productivity, you lose 20% of time just switching back to task, interrupt someone writing email, watch delay before fingers start typing again. Multitasking decreases IQ temporarily. Brooks's law noticed dramatically at end of projects when construction adds manpower. Punch list rework takes 4-25 times more effort to fix versus fixing at time it's noticed, remobilization costs huge. Kingman's formula: cycle time multiplied by capacity utilization multiplied by effects of variation equals overall duration. If electricians can do overhead in 3,000 sq ft area in 5 days at 100% capacity with no variation, but overtime drops them to 60% capacity, that's 8.33 days, then add variation from context switching and communication complexity, now 9-10 days. Felipe's advice: "Fret not if you're getting behind. There are things you can absolutely do and the answer is not just throw more people at it."
What you'll learn in this episode:
Brooks's law from IBM software projects: adding more people or spending overtime when behind schedule doesn't make projects finish earlier, data doesn't support it; short-term overtime under 2 weeks can work, but long sustained overtime is detrimental
Why communication channels explode exponentially: formula n(n-1)/2 means 2 people have 1 channel, 10 people have 45 channels, 200 people on construction site have 19,900 channels, complexity increases faster than headcount
Context switching productivity loss: if interrupted at 100% productivity, you lose 20% of time just switching back to task, interrupt someone writing email and watch the delay before their fingers start typing again
Punch list rework reality: fixing defects after the fact takes 4-25 times more effort than fixing at time it's noticed, remobilization and correction costs are massive compared to doing it right the first time
Kingman's formula proves Brooks's law: cycle time × capacity utilization × effects of variation = overall duration; electricians doing 5-day task at 60% capacity from overtime = 8.33 days, add variation = 9-10 days
Felipe's closing advice: "Fret not if you're getting behind. There are things you can absolutely do and the answer is not just throw more people at it."
"The answer is not just throw more people at it. Stabilize the project so you can optimize it."
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