In epidemiology, **preventable fraction for the population** (PFp), is the proportion of incidents in the population that could be prevented by exposing the whole population. It is calculated as , where is the incidence in the exposed group, is the incidence in the population.^{[1]}^{[2]}

It is used when an exposure reduces the risk, as opposed to increasing it, in which case its symmetrical notion is attributable fraction for the population.^{[citation needed]}