What is absolute top impression share, and is it the same as Impr. (Abs. Top) %?

Google defines the two columns on the same page. Search absolute top impression rate, labelled Impr. (Abs. Top) %, is “the percentage of your ad impressions that are shown as the very first ad among top ads”, calculated as impressions on the absolute top divided by impressions. Search absolute top impression share, labelled Search abs. top IS, is “the impressions that you’ve received in the absolute top (the very first ad among top ads) divided by the estimated number of impressions that you were eligible to receive among top ads”. If you arrived here searching for impressions (absolute top) %, the column you were reading is the rate, and it says nothing about the auctions you missed.

Two counting details sit underneath the rate columns. Google calculates the rate columns using at most one impression per advertiser for a given user search, the most prominent one, so their denominator is not the Impressions figure in your campaigns table, which counts every impression served. And the rate’s count of absolute top impressions includes the very first ad among top ads on the first page or any other page of search results, not only on page one.

The difference matters most when you change a bid. Google does not recommend using the rate columns as a target for setting bids, because they “may decrease as bids increase”: a higher bid can let you enter more competitive auctions in a worse location. The share columns are the ones Google says you can use as a target if you want more of your ads in the first position among top ads. So a falling Impr. (Abs. Top) % after a bid increase is not by itself evidence the increase failed. Read Search abs. top IS beside it before deciding.

Google defines Search top IS as the impressions you received anywhere among top ads divided by the same estimated number of impressions you were eligible to receive among top ads. Every absolute top impression is also a top impression, so by those definitions, for the same rows and dates, absolute top impression share cannot exceed top impression share. Riibon reads the gap between the two as the cheapest read available on whether a campaign is winning the first slot or merely a place among the top ads. Plain impression share is different again: Google divides it by all eligible impressions, not only top ones, so absolute top impression share sitting above impression share is not by itself evidence of a reporting fault.

When the share falls short, Google reports why in two further columns. Search lost absolute top impression share (budget) “estimates how often your ad wasn’t the very first ad among top ads due to a low budget”, and Search lost absolute top impression share (rank) estimates the same thing “due to poor Ad Rank”. Google’s guidance on improving impression share gives a general list of levers, increasing the campaign budget, increasing the bid, narrowing regional targeting and improving ad quality, and does not map a lever to a column. Read each loss column as naming the constraint Google measured, not as a prescription.

What Riibon does with it. Its metric layer marks absolute top impression share and top impression share as ratios that are never summed or averaged across rows, and quotes each one only at the level Google reported it. A ratio of two counts cannot be added across campaigns, and a plain average of it weights a campaign with ten eligible impressions the same as one with ten thousand.

One reporting detail catches people out in spreadsheets. Google does not always return a number. Its documentation notes that a dash against impression share or Quality Score may be down to insufficient data, such as low traffic or new keywords, and the auction insights report does not show insights at all when impression share is less than 10%. A dash is an absence of data rather than a zero, so coercing it to 0 to make a chart work invents a measurement that was never taken. Check what the column actually returned before building a target on it.