Weight Rank is a feature in the Share of Voice report that accounts for the relative importance of placements within search results, i.e., being in 1st is more valuable than being in 5th, and being in 5th is more valuable than being in 10th and so on. 

The Weighting leverages an exponential regression model, using the weekly Amazon SFR report, to identify the Clickshare % given to the Top 3 positions.

For example, if the Top 3 positions for the term 'dog food' took up 70% of the Clickshare %, then the weighting would apply a relatively low value to positions 4 down, as opposed to if the Top 3 had a combined Clickshare % of 10%, then the value for ranks 4 down would be higher.