Some aggregate figures concerning the available data are shown in Table 1. The sizes of both the assortment groups and the product groups vary greatly across the groups. In Season 3, the numbers of SKUs in assortment and product groups ranged from 89 to 322 and from 4 to 195, respectively.

Note from Table 1 that the ratio of realized demand to observed preview demand is reasonably constant over the three seasons. This is important, since Methods 1-3 all use this ratio to forecast at the aggregate level.

It also appears from Table 1 that the total registered lost demand increases over time, especially from Season 1 to Season 2. A possible explanation given by the company is that registration of lost demand has improved over the years. However, no estimates on the effect of improved registration were provided. Therefore, and also after checking that more stable lost demand figures did not lead to substantially different results and conclusions, the registered lost demand figures were left unchanged.