Here's an overview of Leslie Wood's thinking:

HEADLINE:
Advertising campaigns typically deliver 90% of their impressions to segments that have very low responsiveness. Refocussing ad spend on people with whom the creative resonates most powerfully can deliver double the ROAS.

KEY POINTS:
Although brand owners aim for their advertising to reflect the brand strategy, once the creative has been finalised, it often turns out to have a bigger impact on people outside the intended core target.

Frequent brand buyers, and heavy category buyers who buy the brand occasionally, are often the most responsive groups. Likewise, non-category buyers can often provide the biggest sales uplifts.

Long-term sales are driven more by incremental sales from existing buyers than from prior non-buyers, but some creative does a better job of motivating consumers who are not normally highly responsive. To maximise ROI, marketers need to know the sales uplifts by consumer segment for a given campaign and target whichever segment is responding best.

CONSIDERATIONS:
The database for these recommendations comes from CPG frequent shopper data. This might or might not generalise to other types of businesses.