Comparison
Hofstadter's lawvsPlanning fallacy
Hofstadter's law
you padded the estimate for the usual overruns and it still took longer than the padded number.
It always takes longer than you expect, even when you take into account Hofstadter's law. The self-reference is the point: knowing about optimism bias does not remove it, because the correction is applied to a plan that is itself missing the same unknown work. It is quoted in planning as a joke and functions as an argument for empirical forecasting — what similar work actually took — over introspection.
Full entry →Planning fallacy
you estimated the happy path, which is the only version of the work you pictured.
The systematic tendency to underestimate time and cost because we plan from the best-case scenario. It survives experience: people who know they were late last time are still optimistic about this time, because each project feels uniquely well understood. The countermeasure is not more thinking but different evidence, which is what reference-class forecasting supplies.
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