Case file
Subadditivity Effect
- Filed under
- Not Enough Meaning
The charge
Subadditivity effect is assigning higher total probability when a broad category is unpacked into specific parts.
How it operates
Detailed scenarios feel more imaginable and therefore more likely than the abstract whole.
Logged incidents
- Incident 01
A CFO puts 15 percent on supply-chain disruption overall but 10 percent each on strikes, customs delays, and port issues.
- Incident 02
A churn workshop adds separate cause probabilities that exceed total churn risk.
- Incident 03
A founder thinks several channels are each likely to hit and overstates overall revenue odds.
What to watch for
Ask: If I add these detailed probabilities up, do they exceed the total they are supposed to fit inside?
Recommended action
Normalize estimates after unpacking and use mutually exclusive, collectively exhaustive trees.
Known associates
- Mental AccountingMental accounting is treating money or resources differently based on arbitrary labels instead of on total…
- Appeal to ProbabilityAppeal to probability fallacy is assuming that because something could happen or is plausible, it probably…
- Normalcy BiasNormalcy bias is underestimating the possibility and impact of disaster because the present still feels…
- Murphy's Law (as cognitive bias)As a cognitive bias, Murphy's Law is the tendency to overexpect that things will go wrong, often in chains,…
- Zero-Sum ThinkingZero-sum bias is assuming one person's or group's gain must come at another's expense, even when mutual gain…
- Survivorship BiasSurvivorship bias is drawing lessons from the cases that remain visible while missing the failures that…
Source of record