Fig. 2
From: Limitations of the incidence density ratio as approximation of the hazard ratio
Effect of a shorter follow-up duration in the control group on the incidence density ratio (IDR). ID1(t1) is the estimated average hazard in the intervention group up to t1 (black solid line), ID0(t0) is the estimated average hazard in the control group up to t0 (gray solid line); ID0(t1) is the estimated average hazard in the control group up to t1 (gray dashed line), which is not observed; the use of ID1(t1) and ID0(t0) leads to a biased estimate of the hazard ratio (HR)