Instead, ask the project teams to compile a list of all the assumptions that have been made in those initial projections. Then ask them: “Which of these assumptions need to prove true in order for us to realistically expect that these numbers will materialize?” The assumptions on this list should be rank-ordered by importance and uncertainty. At the top of the list should be the assumptions that are most important and least certain, while the bottom of the list should be those that are least important and most certain.
