We’re all bad at estimating the time, cost, and risks associated with a task, and we usually overestimate the benefits. The problem increases with the complexity of the project. This is called The Planning Fallacy.
Here are a few examples to illustrate how this happens.
How long does it take to mow the lawn? For me, between 45 minutes and an hour, depending on how high the grass is, and whether I have to get gasoline. But it also depends on the unforeseen calamity, like when the pull cord breaks, in which case all bets are off. If the spring that retrieves the cord has to be rewound, that can be a hassle.
How long does it take to replace the wax seal under a toilet? If everything goes perfectly, maybe a half hour. But what if the bolts are so rusted that you have to cut them off, which means you need to run to the hardware store to get new bolts, and — as everyone knows — it’s impossible to go to the hardware store once. You always have to make a second trip. What if, while replacing the tank, you discover that the rubber gasket is falling apart and that also needs to be replaced?
To compensate for these problems, follow these three tips.
1. Break down a complicated task into its components so your estimations are more granular and specific.
2. Compare these tasks with relevant experience from previous projects.
3. Don’t make one estimate. Give a pessimistic, a realistic, and an optimistic assessment for each task, and explain when and why each might apply.
Following this method can help to mitigate the effect of the planning fallacy.