Plans are always wrong – everything takes twice as long and costs twice as much. Why is that the case?

• There is not enough slack built into the plan (slack is not acceptable to the management)
• People wanted to win the project in the first place so made unrealistic assumptions (“Are these projects presented to me because they have a positive NPV, or do these projects have a positive NPV because they are presented to me”)?
• Unexpected things happen, incl. stuff that were fully unpredictable (e.g. a Tsunami in Japan)

Plans are inaccurate, but they are not worthless. The value of planning is not so much in the plan itself, but:

• In the communication value: aligning everyone to pull in the same direction
• They help you better understand the opportunities, requirements, dependencies, and risks – plans are a “mental simulation” before the project get started. This helps make the project more successful (or less of a disaster if you did not have a plan).

If you want to improve your plans in a very uncertain environment, the Scenario Planning technique can help.