Blog | June 9, 2022

The Impression Multiplier: What is it, and how does it apply to DOOH?

Unlike most formats within the digital spectrum which operate on a one-to-one basis (meaning one play equals one impression), digital out-of-home (DOOH) requires a slightly more unique approach when determining audience figures. As a one-to-many medium, one play not only equals multiple impressions, but the amount of impressions usually differs depending on the hour, day, and many other factors in the OOH space.

To cater to this unique audience structure in the advancing world of programmatic DOOH, the impression multiplier was introduced to account for the broader reach of any given play on a DOOH screen.

So, what exactly is an impression multiplier, and how is it applied to DOOH?

What is the impression multiplier?

Before we get into the impression multiplier, its important to understand audience impressions in general. An impression refers to the point at which an ad is viewed by an individual person, or played back within an OOH display. A core metric for many forms of advertising including digital, mobile, and OOH, impressions are important as they often determine how much an ad will cost.

The impression multiplier is effectively a DOOH-specific multiplication index applied to each play on every individual screen, giving advertisers an idea of how many impressions are delivered in a single ad play. Because each impression can reach multiple viewers, a multiplier is needed to estimate how many viewers saw the ad, helping advertisers understand the reach of a particular inventory space. 

Contrary to popular belief, the impression multiplier is not one formula applied across all publishers. The index is implemented on a screen-by-screen basis to turn each play into the number of impressions represented by the audience data supplied by each media owner. This means, unlike online and mobile formats, 1000 plays do not equal 1000 impressions. A play can have anywhere from a couple to hundreds of impressions, depending on the format being used. 

What does it look like in practice?

Determining the impression multiplier requires the collection data to give an idea of how many people were around an ad display at a given time. This data can be collected through mobile phone signals, GPS data, camera sensors, ticket sales at an event or stadium, and more. With this information, the amount of people in an ad’s geographic area at a given time can be determined, and the impression multiplier for a particular screen can be calculated.

The cost per mille (or CPM) is a common metric used to purchase advertising based on the number of impressions, known as cost per thousand impressions. With the CPM model, advertisers pay a pre-determined amount to media owners for every 1000 impressions they want their ad to obtain. Without the impression multiplier, the CPM would need to fluctuate throughout the day to better represent the value (and audience) offered by a particular screen. Inevitably, this would mean inventory is underpriced and/or overpriced throughout the day. 

To prevent CPMs from becoming unaffordable at high traffic times, we instead use the impression multiplier to adjust the impressions per play, giving a more accurate representation of the audience delivery and pricing.

Where possible, audience numbers are provided hourly by DOOH media owners. This means that a unique index can be applied to every hour of every day to illustrate the audience in front of a screen at any given time – as per the example below:

In short, audience (or impressions) = play x impression multiplier.

Why is the impression multiplier so important?

Not only does the impression multiplier offer the most effective and efficient means of translating plays into multiple impressions, it also offers a level of flexibility for media owners to stay on top of their audience offerings as and when those figures are effected by external factors. Take COVID for example, where audience numbers plummeted around the world as lockdowns kicked in. Less drastically, other examples could include seasonal changes, changes to the financial markets, or holiday periods. By obtaining the right information on views per screen, media owners can continue to ensure that their inventory remains fairly priced. 

The ability to adjust the impression multiplier by applying realtime, or relatively realtime, percentages to audience figures as they fluctuate ensures that media buyers can take comfort in knowing that they are only paying for the impressions they are actually receiving. With the proper impression data, advertisers can also choose to modify campaigns based on changing external factors, like the ones mentioned above. 

The impression multiplier is a fantastic innovation in the realm of Programmatic DOOH that allows DOOH to align itself with the impression-based buying model while remaining true to the greatest strength of the medium – its capacity for mass reach.

Sebastian Op Vet Held from MyAdbooker gives an amazing, detailed and easily digestible overview of the impression multiplier and its implementation in our latest certification course –  PDOOH Advanced. If you’d like to take part, you can use this link for a 20% discount on our new advanced certification.