Re: don't worry, our ads aren't as effective as we told you
Most ads are about brand awareness and long term impression than immediate sales. Sure you hook a few with your latest deal (cos we all like a bargain) but it's still about the long term.
The companies advertising don't do it for fun, and have a fairly decent set of analytics to measure the effectiveness.
The problem then becomes in making sure your brand is better remembered than the opposition. The rest is just an arms race. For which Feckbook, Gobble et al are eternally grateful.
The most effective advertising is when people don't even realise they've been had. Which is a large chunk of the population.
Note also how careful shops are in directing you round, and how much companies pay to get a certain product on exactly the right spot on the shelf. A difference of up or down one shelf, or being beside the right or wrong product, can have a large impact on sales. All carefully choreographed.
Always makes me smile when people say none of this has never affected them. So naive. We never like to think we've been manipulated. But the reality is most have been in some way.
(Day job has been in Promotional Merchandise for donkeys years so have a vague idea about the subject)