in susan's biography, I can read about susan's choice of marketing perhaps this is what attracted her to marketing, "in which seducing a key demographic is of the utmost importance". I don't understand "a key demographic"? maybe "population-cible"? What do you mean?
A "key demographic" is, as far as I've learned, a target audience for a product or a service. The key demographic for Apple's iPod is, for example, well-off males, mostly singles, with a vintage taste and some spare money at their disposal. (due to what I've read)
The key demographic for specific Delavigne frangrances are, for example, middle-aged women - an for another perfume teenage girls - and so on.
Many products and their marketing experts are quite successful in seducing their key demographic. The Barbie dolls caught on extremely well with little girls (for example).
It's all about seducing: You realize that you need something very badly of which you have never known it existed in the first place.