Advertising works. I used to work for a company that quantified how well it works. Place a newspaper ad and sales increase. Place a newspaper ad and buy an end cap in the store (you don't think products end up on end caps randomly, do you?) and sales increase more. Place an ad, buy and end cap, offer a dicount, and sales will increase even more.
The grocery store club cards are tied to your demographics and to your purchases. The data all gets analyzed and sold back to retailers and consumer packaged goods companies.
"IRI leverages proprietary household-level panel purchase data and unique testing capabilities to provide the most in-depth, comprehensive view of consumer behavior."
Go here to read more:
http://www.infores.com/