Health equity and the fallacy of treating causes of population health as if they sum to 100%

Abstract

Numerous examples exist in population health of work that erroneously forces the causes of health to sum to 100%.This is surprising. Clear refutations of this error extend back 80 years. Because public health analysis, action, and allocation of resources are ill served by faulty methods, I consider why this error persists. I first review several highprofile examples, including Doll and Peto's 1981 opus on the causes of cancer and its current interpretations; a 2015 highpublicity article in Science claiming that two thirds of cancer is attributable to chance; and the influential Web site "County Health Rankings &Roadmaps: Building a Culture of Health, CountybyCounty,"whose model sums causes of health to equal 100%: physical environment (10%), social and economic factors(40%),clinicalcare(20%), and health behaviors (30%). Critical analysis of these works and earlier historical debates reveals that underlying the error of forcing causes of health to sum to 100% is the still dominantbutdeeply flawed view that causation can be parsed as nature versus nurture. Better approaches exist for tallying risk and monitoring efforts to reach health equity.