The role of our Bayesian prior in disagreements over charity assessment

The differences between our approach to charity assessment and others' can be expressed in terms of a different Bayesian prior.

• Our prior over charity effectiveness is unusually pessimistic relative to what we perceive as the norm. Our prior is that a charity is falling far short of what it promises donors. This doesn’t mean we think all charities are failing - just that, in the absence of strong evidence of impact, this is the appropriate starting-point assumption. Many others seem to have the opposite prior: they assume that a charity is doing great things unless it is proven not to be. For more, see our blog post on a conflict of Bayseian priors.
• "Regression to the prior" causes us to put less weight on explicit cost-effectiveness calculations than some others.
  • See our post on why we can't take expected value estimates literally even when they're unbiased.
  • See also our post on maximizing cost-effectiveness via critical inquiry and some considerations against more investment in cost-effectiveness estimates for more information.