Basic relationships. Net benefit is plotted as a function of outcome prevalence. The line represents the relationship with the assumption of a relative risk reduction of 30% and treatment harm of 0%. The line is the maximum net benefit that can be attained at any given outcome prevalence. The x-intercept, or benefit threshold, represents the outcome prevalence at which net benefit will accrue to individuals and the population as a whole. The point of maximum benefit occurs when the outcome prevalence is 100%; at this point, if harm is absent, the net benefit or efficiency of treatment equals the relative risk reduction or efficacy of that treatment. Benefit decreases proportionately as a function of outcome prevalence.