Figure 1.

Model of empirical induction periods. The date of diagnosis for the i^th case is d_i. τ_i is the temporal lag between initiation of the disease (e.g. appearance of the first cancer cells) and diagnosis. ω_i is the induction period when causative exposures occurred. ω_ij is that time interval when the induction windows for cases i and j, ω_i and ω_j, overlapped.