Flight log / Transmission 037

Search impression share: what you're missing and why

Your campaign showed up. Just not every time it could have. Search impression share tells you how often you were on the board, and its two "lost" columns tell you whether the gap is a money problem or a rank problem.

Impression share is one of the few Google Ads metrics that talks about what didn't happen. Clicks, conversions and cost describe the auctions you won. Impression share describes the ones you could have been in and weren't.

That makes it useful and easy to misread. This guide covers what each impression share metric measures, how to tell a budget gap from a rank gap, what top and absolute top impression share add, how exact match impression share exposes broad match drift, and when chasing a higher number is a waste of money.

What is search impression share?

Google defines search impression share as the impressions you've received on the Search Network divided by the estimated number of impressions you were eligible to receive. The key word is estimated. Google's impression share help page says eligible impressions are estimated using "many factors, including targeting settings, approval statuses, and quality."

A few mechanics worth knowing before you read the column:

• It excludes Search partners. Google says Search partners don't distinguish between top and other placements and aren't included in impression share data.
• It lags. Google says the data can take 24 to 48 hours to update, so yesterday's number is not final.
• It's reported per campaign type. Search, Display and Shopping impression share are reported separately and not rolled into one account number.
• A blank means not enough data. Google says low-traffic or new keywords may show a dash instead of a percentage.

Say a campaign received 4,700 impressions and Google estimates it was eligible for 10,000. Search impression share is 47%. The other 53% went somewhere, and that's what the lost columns explain.

Which impression share metrics does Google Ads report?

There are more columns than most people use. Here are the ones that matter for Search campaigns, with Google's definitions paraphrased.

Google's documentation is explicit that lost IS (budget) is a campaign-level metric, because budget is set at the campaign level. You won't find it on the ad group or keyword tab, and it was removed from saved ad group and keyword reports in June 2022.

Lost IS (budget) vs. lost IS (rank): what's the difference?

These two columns are the diagnosis. Whatever share of eligible impressions you didn't win, Google attributes to one of two causes.

Search lost IS (budget) is, in Google's words, "the percentage of time that your ads weren't shown on the Search Network due to insufficient budget." Typically that means the campaign was paced or ran dry before the day was over.

Search lost IS (rank) is "the percentage of time that your ads weren't shown on the Search Network due to poor Ad Rank in the auction." Ad Rank is calculated from your bid, the quality of your ads and landing page, Ad Rank thresholds, the competitiveness of the auction, the context of the search and the expected impact of assets. Money alone doesn't fix it.

The fastest way to see the difference is to watch what happens when you change one lever. The chart below is a hypothetical B2B search campaign where the budget was raised in week 5.

In this illustrative account, the budget increase did what it should: lost to budget fell from the low 20s to 8%. Lost to rank barely moved. That's the pattern to look for. If you raise budget and only the budget column moves, the remaining gap is a rank problem, and the next dollar of budget won't buy it back.

Fixing a budget gap

A budget gap is the easy one to diagnose and the one to question hardest. Before raising the budget, check whether the campaign is already spending on searches you don't want. Cutting waste through the search term report can free budget without adding any. If the traffic is good and the cost per conversion holds up, then the budget is the constraint and raising it is a reasonable test.

Fixing a rank gap

A rank gap means you were eligible but outbid or out-qualified. The levers are the Ad Rank inputs: a higher bid or target, more relevant ads, better assets and a landing page that matches the search. That last one is where many accounts leave rank on the table. Our guide to improving Quality Score covers the ad and landing page side in detail.

What do top and absolute top impression share tell you?

Search impression share counts an impression anywhere on the page. Two more metrics narrow it to position.

• Search top IS counts impressions anywhere among top ads, divided by the impressions you were eligible to receive among top ads.
• Search absolute top IS counts only impressions as the very first ad among top ads. It is always the smaller of the two.

Both have lost-to-budget and lost-to-rank versions that work like the main pair. Google also distinguishes them from Impr. (Top) % and Impr. (Abs. Top) %, which describe where your impressions landed rather than how many you could have had. Google's top metrics page advises against using the impression rate as a bid target because it can drop as bids rise. Use top IS when the question is "how often am I at the top?"

Position matters most where the first result does the converting. Here is a hypothetical comparison of a brand campaign and a non-brand campaign in the same account.

In this illustrative account, the brand campaign is at the top almost every time it shows, and the gap between top IS and absolute top IS is where a competitor bidding on the brand name would show up. The non-brand campaign shows on fewer than half of eligible searches and is the first ad on 12%. Whether that 12% is a problem depends on what the first position is worth, which is a cost question, not a pride question. For who's taking those positions, read the room with auction insights.

What is exact match impression share for?

Search exact match IS is the impressions you received on searches that exactly matched your keywords, divided by the estimated number of exact match impressions you were eligible for. Google says it's only available for Search Network campaigns.

Its job is comparison. Google's help page puts it this way: compare it with overall impression share to "determine whether your impression share is low on all searches" or only on searches that broadly match your keywords. If your exact match IS is high and your overall IS is low, you're winning the searches you meant to target and losing the loosely related ones. Google's suggested next step in that case is a search term report.

A related view is keyword-level impression share grouped by match type. The hypothetical campaign below has the pattern you'd expect when broad match keywords reach for a wide set of queries.

Read this one carefully. The broad match row loses most of its eligible impressions to rank, which sounds bad until you remember it's eligible for a far larger and looser set of searches. A low share there may simply mean your bids aren't competing hard for loosely related queries, which is often what you want. The remainder in each row, the share not shown in either bar, is lost to budget, which Google only reports at the campaign level.

What is a good search impression share?

There's no universal target, and any single benchmark number you see quoted should be treated with suspicion because it mixes brand, non-brand, industries and budgets. The useful question is narrower: is the next impression worth what it costs?

The cost of impression share isn't linear. The last few points usually come from the most competitive auctions, the highest positions and the least efficient hours. The illustrative curve below shows the shape that tends to appear when an account pushes for more share on a competitive non-brand term.

In this hypothetical, going from 40% to 60% share costs about 75 cents more per click. Going from 80% to 95% costs nearly $5 more. If the conversion rate on those extra clicks doesn't rise with the price, the high score is a loss. A rough rule of thumb that holds up in most B2B accounts: aim high on brand, where the clicks are cheap and the downside of absence is real, and let non-brand share land wherever cost per conversion stays acceptable.

Google offers a bid strategy built for this: Target impression share, which sets bids to show your ad among top ads, as the first ad, or anywhere on the page, with a max CPC bid limit as the safety rail. It's useful for brand protection. On non-brand terms, it optimizes for visibility, not for conversions, so treat it as a deliberate choice rather than a default.

How do you diagnose an impression share gap?

Match the pattern to the move. This is a starting point, not a decision tree to follow blindly.

A practical routine: add the impression share columns to your campaign view, set the date range to the last 30 days, sort by cost and read the top 10 campaigns. Note which column dominates each gap. Then drill into the rank-limited ones at the ad group and keyword level. It fits inside any routine account audit.

Where impression share misleads

• The denominator is an estimate. Google says changes to your bids, quality or its own ad systems can change the set of auctions you're estimated to be competitive in. Small swings don't necessarily mean anything, and Google says as much.
• Maximize conversions breaks the budget column. Google's Maximize conversions help page says it doesn't recommend using the Lost IS (budget) column with that strategy, because the strategy is designed to spend the full daily budget and is "limited by budget" by design. Google points to the budget simulator instead. If you're weighing bid strategies, see Target CPA vs. Maximize Conversions.
• Search partners are invisible here. If a campaign runs on Search partners, a chunk of its traffic isn't in any of these numbers.
• Higher share isn't the goal. Impression share is a diagnostic. A campaign at 35% share with a healthy cost per qualified lead can be in better shape than one at 85% that's buying every expensive click in the category.
• It says nothing about the click after. Winning more impressions sends more people to the same landing page. If that page converts poorly, more share just means more of the same result at a higher price.

The short version

1. Read the two lost columns together. They tell you whether the gap is money or rank.
2. Question budget gaps before funding them. Clean the search terms first.
3. Fix rank with relevance before bids. Ad and landing page quality are Ad Rank inputs, and they compound.
4. Use top and absolute top IS for position questions, especially on brand terms.
5. Compare exact match IS with search IS to see whether you're losing the searches you meant to win or only the loose ones.
6. Stop where the next point costs more than it earns. That's your real target.

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