The Planning Fallacy

2 min readJul 5, 2018

Why is that we can never seem to stick to a plan?

The Sydney Opera House is one of the world’s most recognisable and iconic buildings.

It’s the jewel in the crown of the stunning harbour city.

With a design inspired by the segments of a cut orange, it attracts millions of tourists each year.

Scheduled for completion in 1963 at a cost of $7 million (AUD), it was actually only completed in 1973 at a cost of $102 million (AUD).


Clearly, those responsible for planning its construction were not doing their job properly.

And they’re not alone.

The Scottish Parliament in Edinburgh was delayed by 3 years and ended up costing nearly ten times its original budget. The development of the Eurofighter Typhoon was also delayed by many years and cost taxpayers 75% more than was originally planned.

What’s going on here?

The simple answer is that human beings are notoriously bad at predicting how long a given task will take.

This is known as the planning fallacy.

We tend to be overly optimistic about the time it takes to do something — this is because there are many factors that are outside our control as well as factors that we might not be aware of at the time of planning.

This explains why it is almost impossible for any large scale project to be delivered on time and on budget.

So what can we do about it?

When planning anything, triple the amount of time you instinctively allotted to completing the task. This is most likely the amount of time it will take in reality.

This is a particularly helpful ‘rule of thumb’ if you are doing work on behalf of clients.

Under promise. Over deliver.




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