[creer]

Why do you think so many things are not measurable?

It's very hard to poll or measure things to within a fraction of one percent with most audiences. But that's not what's needed for advertising. And in marketing you probably don't care about that - it's in the noise. You do care of "significant" changes and you can of course measure both positive and negative influence.

Even negative influence in people who aren't yet customers, or have never heard of your company, and (preferably) have never seen your ad. For example through a polling survey. Funny enough, such a poll is probably an effective ad campaign in itself in some cases! You can also measure opinion strength about advertising in general. It's more nuanced than you think. Which unfortunately leads marketing departments to commit atrocious injury to good taste. Agreed there.

> No one rationally proposes that someone spends a hundred dollars on advertising to generate $100.10 in revenue is somehow a good use of money.

Of course not, and yet they spend far more than that, to good (measured) effect.