Here's an overview of Byron Sharp's thinking:
Growth is driven by building brand penetration which is achieved by being easy to find and establishing high levels of 'mental availability’.
People don’t usually think much about their purchases. They quickly pick whatever seems a good choice in the moment. They see all brands (within a well-defined category) as much the same, and aren’t emotionally attached to some more than others. To grow, brands need to increase:
a) Physical availability: being widely available and easier to buy at the right times/places.
b) Mental availability: coming to mind more often when people think about a purchase need/occasion (or ’Category Entry Point’) or when they come across the brand.
Mental availability can be increased by using a set of distinctive assets (such as colours, logos, slogans, jingles and characters) across touch-points and consistently over time.
Attempting to characterise and target people who will be most responsive to your advertising makes little sense because a brand’s heaviest buyers in one period often become light buyers in a later period and vice versa. For this reason, advertising should be targeted to reach as many category buyers as possible and loyalty programmes are not worth the investment. Also, since at any one time, the majority of category buyers don’t currently need to buy the category, advertising should be ’always on’ so that when people next buy the category, they will have been reminded of the brand recently.
Validation of the relationship between penetration and market share is extensive. The principle of maximising reach with advertising is widely supported. Professor Sharp’s conclusions challenge widely held beliefs within the marketing community about the importance of brand differentiation and the benefit of putting more advertising weight behind more responsive audiences.