trailComplex risk analyses historically exhibit error rates exceeding their claimed risk bounds
The probability of error in a safety argument bounds the confidence it can provide about low-probability risks
A flawed safety argument provides little evidence about the risk it assesses
Safety arguments with minor flaws often remain approximately correct
Cross-domain track record of exceeded risk bounds· for
Pre-Challenger official estimates of Space Shuttle failure risk were far below the realized failure rate
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Nuclear probabilistic risk assessments predicted core-damage frequencies well below the observed historical accident rate
Published probabilistic risk assessments for nuclear power plants typically estimated core-damage frequencies of about one in 10,000 to one in 100,000 reactor-years or lower
Core-damage accidents in commercial nuclear reactors have occurred historically at a rate on the order of one per few thousand reactor-years
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The historical core-damage record is dominated by early-generation and Soviet reactor designs outside the scope of most probabilistic risk assessments
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Bank value-at-risk models understated the frequency of extreme losses before the 2008 financial crisis
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Conservatism and selection effects· against
Regulatory risk assessments commonly use conservative assumptions that overstate risk
Regulatory agencies deliberately adopt conservative, health-protective default assumptions in risk assessment
Compounding multiple conservative assumptions causes regulatory risk estimates to substantially exceed actual risk
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claim · empirical · derivedA factual claim that rests on inference from other evidence rather than direct observation.constitution →claim page ↗︎
Complex risk analyses historically exhibit error rates exceeding their claimed risk bounds
↑SupportedEvidence favors the claim, but the chain is incomplete or the sources are secondary.constitution →credence 0.80Credence, from 0 to 1: the Steward's probability that the claim, as stated, is true. Stated only where a single number is an honest summary; normative and evaluative claims usually carry none.constitution →
3depended on by
this rests on ↓
claimA box is a claim: a single proposition the graph assesses, with its own page and map. Click any claim to centre the map on it.constitution →argumentA pill is an argument: one line of reasoning stating how the claims beneath it combine to bear on the claim above it, for or against. Arguments are not destinations; click their claims to explore.constitution →✓verifiedThe claim traces to reliable primary sources through a clear chain of evidence.constitution →↑supportedEvidence favors the claim, but the chain is incomplete or the sources are secondary.constitution →⇄contestedCredible evidence or argument exists on multiple sides.constitution →○unsupportedNo credible evidence found, though the claim is not contradicted.constitution →✕contradictedAvailable evidence weighs against the claim.constitution →?unknownInsufficient information to assess.constitution →◌unassessedNo current assessment. Attention goes where its expected value is highest and someone funds it; nothing has funded an assessment of this claim yet, and anyone can.constitution →verified factopen questionvalue premisesupportsthis provides evidence for the parentsteward instructions →contradictsthis argues against the parentsteward instructions →assumesbackground the parent's framing takes as givensteward instructions →requiresa load-bearing premise: the parent is false without itsteward instructions →Fig. Detail falls off with distance; every claim is an address.