How individual brands penetration relate to portfolio market share

In manufacturer brand portfolios, how do the penetrations of the individual brands relate to portfolio market share and does buyer overlap matter? And the online share of the grocery market continues to stabilise.

1. On average for 2 brand portfolios, for every one point increase in the summed penetrations, share rises by 0.65% points. This increase is even higher for less frequently bought categories and lower for frequently bought categories where brand repertoires are larger.
2. On average for 2 brand portfolios, the 0.65 relationship between the summed penetrations of the two brands and their total share is not significantly impacted by whether each brand’s buyers are unique or whether they overlap.
3. Online share peaked early in 2021 but like in 2020 this has dropped back and now stabilised at very similar levels to the first half of 2020. Older age groups returning in part to in-store shopping is one of the factors.