Average daily average respiratory count, by week, for week 20 through week 71. The same data as in Figure 1, but only for week 20 through week 71 in 1993 and for week 20 through week 71 in 1994. Note that the peak onset, shape, and duration varies each year in the real data (top left) and in data simulated from the hierarchical model (top right), but not in data simulated from the nonhierarchical model (top middle). The forecast errors arising from using Eq. (1) to forecast (Method 1) and a smooth curve fit to the errors illustrate strong serial correlation in the corresponding bottom left and right plots (and very mild or negligible serial correlation in the middle plot). Each bottom plot shows forecast errors for the same period, weeks 20 through 123, without overlaying successive years.