What is Search lost IS (rank)?

The column is labelled Search lost IS (rank) in the interface. Google’s own definition is “the percentage of time that your ads weren’t shown on the Search Network due to poor Ad Rank in the auction”. Read that as written. It is a measure of time, and it attributes the loss to Ad Rank.

That unit is what makes the column easy to misread. Impression share, sitting next to it, is defined as the impressions you received divided by the impressions Google estimates you were eligible to receive, which is a ratio of impressions. One column counts impressions and the other counts time. Google does not publish a statement that impression share and the two loss columns sum to 100 per cent, and the units it uses cut against the idea. Treat them as three separate measurements of the same campaign, not as three slices of one pie.

There is one documented trap worth knowing before you read anything into this column. Google states that “Lost IS (rank) won’t be shown on your Ad groups tab if you ran out of budget at any point during the date range being examined”. So a date range in which the campaign hit its budget, even once, cannot answer the rank question at ad group level at all. The number is absent rather than low, and an absent number is not evidence of a healthy Ad Rank.

The Display Network has a column with the same shape and a separate definition: Display lost IS (rank) is “the percentage of time that your ads weren’t shown on the Display Network due to poor Ad Rank”. It is a different network and a different measurement. Google reports impression share metrics separately for each campaign type and does not aggregate them across the account.

What the column does not do is name a fix. Google describes Ad Rank as recalculated every time an ad is eligible to appear and again when it competes, with ad quality considered in establishing it and the bid able to affect it, but it does not publish a mapping from a lever to a loss column. A loss attributed to rank tells you which constraint Google measured. It does not tell you that a budget change would be inert, and we do not claim that here, because Google does not.