Interesting post over on 43Folders on planning and task estimation. I've certainly experienced theses problems in the past but hadn't heard them described as the planning fallacy or optimism bias. The suggested ~44% buffer to add is quite depressing but probably close to true based on my experience. That means in a typical 5 day work week, you'll be lucky to do useful work for even 3 of them.
The flip side of planning is probably something we've all experienced too. You do your best to come up with a realistic schedule, then you are told that that is unacceptable and to reduce it to a wildly unreasonable, unrealistic estimate. Everyone knows it will be unachievable, but that's what you work towards. No wonder so many projects slip - they finish right around when they would have finished with realistic planning. Now that isn't to excuse projects on a terminal death march or those that have gone wildly out of control. But so often, I've been on projects where the end date was set before the planning was done.
In fact, I think in those cases, a realistic schedule might mean the project would never start, so everyone puts on their rose-coloured glasses and agrees to an insane schedule, that meets the deadline. Then the project starts to slip, often before anyone can even do any work it will be late. Over my career I've collected metrics on the various projects I've worked on, formally and informally. I've found quite a bit of resistance to using this real world project data for subsequent planning sessions. Mostly that's been the case when a certain schedule was required, with set number of people and the nasty reality of past experience was meaning the numbers wouldn't add up correctly. Those projects finished when we originally thought they would too.
So how do we move beyond this? Is it really that we are so bad at estimating how long things will take? Or that we can't accept the numbers that we come up with because of the time to market pressures and realities of the market place? Do the planners want to know the truth right at the start, or deal with the successive revelation of the nasty reality over time? Execution by one thousand slips or just planning business as usual?
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