Cumulative incidence

Cumulative incidence is a measure of frequency, as in epidemiology, where it is a measure of disease frequency during a period of time.

Cumulative incidence is calculated by the number of new cases during a period divided by the number of people at risk in the population at the beginning of the study.

It may also be calculated by the incidence rate multiplied by duration.

$$CI(t)=1-e^{-IR(t) * D}\,$$