Precision is less valuable when the measurement is larger.

The very first piece of software I optimized, I started with “One Mississippi”, moved to a stopwatch app on my PDA, before I ever bothered with instrumentation. Because any idiot can tell 2 seconds from 3, that a boat won’t fit in the garage, or that more than double is way less than ten.

Ironically, if Brooks had said 3x instead of 10x, he might still be right and we’d have invested more in measuring things.