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Is Impression Share a Valuable Metric?

Is Impression Share a Valuable Metric?

Written by enCOMPASS Agency

One of the biggest benefits of Pay-Per-Click (PPC) advertising is that it provides advertisers with countless data points. By prioritizing and interpreting these data points correctly, advertisers can make smart changes to their strategy, maximizing their return on investment.

Crucial to this process is understanding what different data points mean, and how valuable each one actually is. As a general rule, the enCOMPASS team believes that no one metric is sufficient for making big decisions about an ad campaign. Rather, it’s important to have a more comprehensive view of the available data points, drawing on many different pieces of information to guide strategy.

This is certainly the case with impression share, a metric that is sometimes touted as the be-all and end-all of PPC. Our take is that impression share may be useful, but only when it is correctly interpreted as one piece of a larger data set. Making decisions based on impression share alone can be dangerous and often leads advertisers to making decisions that can be catastrophic.

Why is that, exactly? Let’s take a closer look at impression share, including both its usefulness and its limitations.

What is Impression Share?

According to Google, impression share may be defined as “the percentage of impressions that your ads receive compared to the total number of impressions that your ads could get.” In other words, your impression share will always be a percentage, somewhere between zero and 100, and it’s arrived at via a simple mathematical equation: Total impressions divided by the number of impressions you were eligible for.

Google goes on to explain that, by using impression share as a data point, you can theoretically arrive at a useful conclusion about whether your ads might be seen by more people, if only you increase your bid or your budget. While there’s some truth to that, it’s important to acknowledge the ways in which impression share is a flawed, imprecise metric.

Problems with Impression Share

Perhaps this all sounds valuable, but there are some significant issues with using impression share as a metric. Even within Google’s own explanation of impression share, they acknowledge multiple times that it’s just an estimate, and one that may be influenced by a number of questionable factors. Consider this admission from Google (with emphasis added): “Impression share includes all auctions where your ad showed, and all auctions where your ad is competitive enough to show. For example, it could include auctions where your ad could show at twice its current bid, but could exclude auctions where your ad is estimated to need a 1,000% bid increase in order to appear.”

Indeed, one of the reasons why impression share is such a fuzzy metric is that your eligibility for impressions is constantly going to be fluctuating. Every time you enter an ad into an auction, you’ll need to make a new bid and also receive a new quality score. These factors can both have a significant impact on the impressions for which your ad is eligible.

To put it differently, a low impression share may point to a number of potential issues. Sometimes, it may simply mean that your bid was too low, and thus your ad wasn’t shown. But in other cases, it may mean that your bid was so low that the ad wasn’t even eligible to show, which is something very different.

Why is Impression Share So Popular?

Despite the fact that impression share represents a rather fuzzy estimate, it remains a cherished metric among many advertisers. There are a couple of reasons why this is the case.

One, low impression share can seem like a problem with an easy fix… and for advertisers who love problem-solving, that can be appealing. If you’re getting low impression share, it’s simple enough to say that you just need to throw some more money behind your bids in order to increase the impression share. And sometimes, that may be the case. In other instances, though, more money isn’t the issue; the issue may have a lot more to do with ad quality.

Additionally, by achieving a high impression share (say, 100 percent), advertisers can feel as though they are not missing out on any sales opportunities. Advertisers are by no means exempt from the fear of missing out, and seeing a high impression share is one way to assuage that fear.

The Problem with Using Incomplete Data

Our main point here isn’t that impression share is a bad metric so much as it’s an incomplete one; and, by using it as the sole basis for big campaign decisions, advertisers may really be doing themselves a disservice.

Keep in mind that impression share only takes into account a specific ad campaign; it doesn’t take into account your overall strategy. In other words, it’s possible to have a low impression share but still be running a very healthy, effective campaign. Your low impression share may actually be the result of good coverage for keywords in other parts of your strategy.

But if low impression share can obscure a strong campaign, the opposite is true, as well: High impression share may cause you to think your campaign is more effective than it really is. Imagine a movie theater with just one person in the seats; in this situation, you could say that the movie being shown is getting a 100 percent impression share. That’s all well and good, but appealing to an audience of one usually isn’t as meaningful as achieving broader outreach.

Here it’s worth noting that, at enCOMPASS, we typically use a lot of keywords in our PPC campaigns, and we optimize bids continuously based on the results for each keyword. We consider this to be one of the big benefits of our platform. However, what it means is that our impression share is likely going to be lower when you look at the keyword list as a whole. And even if you focus on just a couple of keywords, the impression share could be lower because of decisions we make to maximize a client’s budget. All of this is by design, allowing us to focus on the most important impressions (e.g., the ones that lead to conversions) rather than focusing on sheer volume of impressions. Let’s look at a specific example of two advertisers with the same budget:

Advertiser A:
Impression Share: 80%
# of Keywords in campaign: 20
# of conversions per month: 100

This advertiser might feel as though their campaign is running great, given their 80% impression share. However, notice that they are only bidding on twenty keywords so it’s rather easy to report a high impression share. However, if there are 300 keywords that they should be bidding on to achieve optimal performance, then impression share is not telling them much. In fact, it is giving them a false sense of confidence because it is not taking the total number of keywords they should be bidding on into consideration.

Advertiser B:
Impression Share: 30%
# of Keywords in campaign: 300
# of conversions per month: 300
Impression share of Advertiser A when compared to all 300 keywords: 12%

This advertiser could see a 30% impression share and feel like they need to do more. However, with the same amount of budget, this advertiser is showing three times the conversions because they are bidding on a much broader number of keywords. This campaign is much better optimized giving the advertiser more impressions for keywords that advertiser A will never show up for, because Advertiser A is only bidding on 20 keywords instead of the 300 they should be bidding on.

When considering Impression share, rather than looking at your own impression share in isolation, try comparing your impression share for all of the keywords in your campaign, to your competitor’s impression share for that same group of keywords. These findings will give you a more accurate picture of how you truly compare in your market and help you find opportunities without chasing your impression share “tail”.

Finally, we should point out one of the big ironies of impression share: If you make campaign decisions based on this one metric alone, it can actually cause your impression share to decrease significantly! The reason for this is that if you put a lot more money into your campaign/daily budget, your bids will likely increase and therefore make you eligible for a lot more impressions; this often has the effect of making your total share of impressions stagnate or even decline.

A Better Way

Any time you’re making big decisions about an online ad campaign, it’s crucial to work with a full set of information, and to interpret data points in relation to one another. Impression share may be a piece of this puzzle, but it shouldn’t be seen as the full picture. At enCOMPASS, we’re proud to have a platform that takes a more comprehensive and holistic view of your ad strategy.

Questions about your ad metrics? We’d love to chat about this further. Reach out to the enCOMPASS team any time.