The Seductive Danger of Impression Share

Advertising is all about targeting, right? And once you’ve found a targeted audience, you want to get your ads in front of all of that audience. This is the thought process behind Impression Share, that often elusive, seemingly golden metric that Google dangles before us in AdWords reporting.

And why wouldn’t Impression Share be important? You certainly don’t want to cede valuable targeted eyeballs to your competitors, do you? Why, that would be leaving money on the table, so the higher Impression Share the better!

Not so fast.

As we continue our decade-and-a-half long transition from negotiated media buying to auction-based media, it’s worth taking a second look at Impression Share, as nothing may be quite so seductive, or quite so dangerous in our everyday marketing metrics.

Impression Share is an easily understood metric. What percentage of the available audience were you able to put your ads in front of? Impression Share measures exposure as the percentage you successfully marketed to. Simple.

The problem is that, unlike negotiated media where delivered impressions are specifically negotiated (with a make-good period typical when there is a shortfall), in the auctions it usually takes higher bids to capture that elusive missing percentage of Impression Share. That incremental cost may not be worth it. In fact, going after higher Impression Share may cause you to take a profitable campaign into unprofitability.

This is because successful auction-based advertising is performed by knowing how much to pay for advertising relative to the value of the revenue generated by that investment. Unlike the old school media buying paradigm of the most-eyeballs-for-the-lowest-cost, auction-based media is hyper-targeted, competitive, and dynamic. One of the best results of knowing what to pay for advertising is knowing what not to pay.

Which brings us back to Impression Share. If you are getting 100% Impression Share on a wide variety of keywords, chances are you are paying too much. It’s rare for a company to be able to monetize traffic so well that ad positions that garner 100% Impression Share are profitable across the board.

So, what good is Impression Share? If you are optimizing a campaign using value-based segmentation and value-based bidding (as you should be), Impression Share is a great metric for understanding the untapped opportunity available, if conditions change to allow for better monetization. This can happen through focused conversion improvement testing, or speaking to higher-than-average value customers. However you improve the math of conversion, the untapped Impression Share gives a sense of the size of the additional audience that may be out there.

If Impression Share is so dangerous, why does Google promote it? The answer is probably obvious. The only one who always wins the Google auctions is Google. Impression Share promotes tactics that get Google more advertising dollars. But used correctly, Impression Share can be a helpful metric to gauge an additional available audience, but one that can only be tapped into if you can get the math of cost -> conversion -> value to work.