Every message has an intended audience and advertising only works when the ones who see the ad are the one who were intended to. Most advertising is very irrelevant and that’s why people hate it, because it has nothing to do with them. Nobody complains about seeing relevant ads because they are helpful and add value, like Cindy Gallop says “Everyone hates advertising in general, but we love advertising in particular.”
That’s why getting your message to just the right person at just the right time is worth a lot of money – hence Google making billions on allowing advertisers to show their ads to just those people who are looking for it. But Google ads only work when someone knows to search for what you sell in the first place. There are a lot of other advertising mediums that don’t promote relevancy as much. Most innovation in online marketing is in trying to make ads more relevant. Two metrics that can be used to measure relevancy are conversion rate and click through rate.

Conversion rate measures the relevancy between a landing page and the ad promoting it. There is a certain level of expectation that someone has before when they click on an ad, and if that expectation isn’t met, or isn’t relevant, they leave and conversion rate goes down.

Click through rate measures the relevancy between an ad and its placement. Ads that are shown but don’t get clicked get low click through rates and signal irrelevancy.

Low conversion rate and low click through rate should be signs that you’re doing it wrong  – the right person is not seeing the right message. I think the majority of the effort spent on optimizing marketing should be focused on increasing relevance.