The uniqueness trap and why intelligent people make bad project decisions

The paper discussed here is “The Uniqueness Trap” by Bent Flyvbjerg et al., published in Harvard Business Review (March–April 2025).

You can access the full paper here:

https://hbr.org/2025/03/the-uniqueness-trap

An academic version is also available via SSRN  .

The central argument is simple and uncomfortable. Project leaders routinely believe their projects are unique. This belief is strongly correlated with poor outcomes.

Across a large dataset of IT projects, the authors show that the more “unique” managers believe their project to be, the greater the cost overruns and schedule slippage. A one-point increase in perceived uniqueness corresponds to an average five-percentage-point increase in cost overrun. Projects rated as maximally unique were far more likely to exceed budgets by more than seventy-five percent  .

What matters is not whether a project is unique. What matters is whether leaders treat it as if it is.

Why uniqueness feels convincing

Many projects feel unique because they are complex, politically sensitive, or new to the people leading them. The paper shows that these factors correlate with perceived uniqueness, but they do not explain the overruns. The bias itself does.

When the authors tested supposedly unique projects against large reference datasets, every one had clear precedents either within the same organisation or across the same industry. None were genuinely without analogy  .

This is a textbook example of what Daniel Kahneman calls the inside view: decisions based on personal experience, local context, and narrative detail rather than statistical evidence and base rates.

Clear links to PRINCE2

This paper aligns closely with PRINCE2, even though it never mentions it explicitly.

1. Business Case

PRINCE2 requires a continued business justification based on realistic costs, risks, and benefits. The uniqueness trap directly undermines this principle. When leaders assume a project has no precedent, estimates are built on optimism rather than evidence.

The paper reinforces why PRINCE2 insists that the Business Case is not a one-off document but something that must be challenged and refreshed as learning accumulates.

2. Learn from Experience

PRINCE2 explicitly states that projects should learn from experience, including from previous projects, programmes, and external sources.

The uniqueness trap explains why this principle is so often ignored in practice. If a team believes its project is unprecedented, learning feels irrelevant. The paper shows that this belief is almost always wrong and measurably harmful  .

3. Manage by Stages

Stage boundaries in PRINCE2 are designed to create pause points for reassessment. The outside-view techniques proposed in the paper, such as reference class forecasting and premortems, fit naturally at these boundaries.

They provide structured ways to challenge inside-view assumptions before further commitment is made.

4. Risk management and tolerance

PRINCE2 distinguishes between uncertainty and risk and emphasises the need to define tolerances. The paper shows that perceived uniqueness systematically leads leaders to underestimate both average risk and tail risk.

This helps explain why tolerance breaches often surprise senior stakeholders. The estimates were fragile from the start.

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5. Tailoring, not exception thinking

PRINCE2 encourages tailoring the method to the project environment. The uniqueness trap shows what happens when tailoring becomes an excuse for abandoning comparison altogether.

Tailoring should adjust governance and controls, not suspend learning from precedent.

Why this matters for students

This paper is a reminder that frameworks like PRINCE2 are not bureaucratic rituals. They exist to counter predictable human biases.

The most dangerous sentence in project management is not “we lack data,” but “this is different.” Flyvbjerg et al. show that when leaders believe that sentence, cost overruns and failure become far more likely.

For students, the lesson is clear. Good project management is not about confidence. It is about calibration. The discipline to look outward, compare honestly, and accept that your situation is rarely as special as it feels.