Figure 6.

Data structure of our data and model. Available observations spanned by $n_{0,0}, n_{T,0}, n_{T-D,D}$ and $n_{0,D}$ are in the right-angled trapezoid $O_T$ while the triangle $U_T$ spanned by $n_{T,1}, n_{T-D+1,D}$ and $n_{T,D}$ represents the cases that occurred but not yet reported. Delays greater than $D$ are rare and ignored.