The OOH industry has long acknowledged that just because you can see an ad does not mean that you will see it. People often tune out advertising, especially in busy urban environments where ads compete with other stimuli. Therefore, when planning, media advertisers must consider the difference between viewable and viewed ads.
Out-of-Home (OOH) strict definitions for Viewable Impressions have existed for a long time. The advertising industry has gone further since the mid-90s, using eye tracking studies to calculate the realistic likelihood to see these Viewable Impressions. Today, OOH advertisers no longer buy viewable contacts, instead they buy ‘Visibility Adjusted Contacts’ (VAC).

What do advertisers pay for?

It seems that other media channels are waking up to the dual issues of Viewability and Viewing, while Viewability measurement is still a hot topic within the digital industry. Should advertisers pay for ads that consumers have no realistic chance of seeing?

Consequently, IAB (Interactive Advertising Bureau) has introduced consistent definitions of what counts as a ‘viewable impression’ online. An ad only qualifies as being viewable if 50% of its pixels are continuously on screen for 1 second or more, or at least 2 seconds in the case of video playback.

Viewing versus Viewability: It’s half the story

But the OOH experience suggests that measuring Viewability alone is not enough. Online ads on both desktop and mobile exist in an environment which is just as busy as a typical street. In the case of TV or Cinema ads, content is typically punctuated by advertising that dominates the screen; one might call ‘sequential’ advertising. However, online and OOH ads take up only a part of the visual field and are served next to other attention-grabbing content. In contrast to ‘sequential’ media, you might call this ‘simultaneous’ advertising.
In mobile and desktop environments, just as in OOH environments, people have a choice about what to look at - they could look at the ad, but they don’t have to. Advertisers must learn about their audience’s attention and behaviour, and media owners must measure the realistic attention within their medium. VAC is an expression of ‘reality of attention’; the measure goes beyond Viewability and instead, we finally have a way to measure actual Views.

Applying OOH Measurement to other Media | The Research

But what would happen if we applied the VAC standards to online advertising, desktop and mobile? JCDecaux collaborated with experts in Attention Technology, Lumen Research, to investigate cross-media application of Viewed Impressions. The key question was can one define the likelihood to actually engage with viewable advertising across both Online and OOH advertising?  The goal of the study was to provide a common currency of attention across different media and help media planners evaluate the actual reach of campaigns. 

Viewability Rates

To calculate VACs (Visibility Adjusted Contacts), first it was necessary to calculate viewability rates. The rates calculated through Lumen’s studies were in line with IAS data: Desktop 64% in Lumen data vs. 61% in IAS data, Mobile 43% in Lumen data vs. 44% in IAS data.

For static OOH posters, audience measurement protocols ensure Viewability is 100%. For DOOH ads, a simple formula can be applied to calculate the Viewability of an ad on rotation. This factors in the length of the ad, the number of ads on rotation, and duration of audiences passing. 

Applying the convention of 6 x 10s ads in the above formula, along with typical passage durations, gives the DOOH Viewability rates.

Realistic Likelihood to See (RLTS)

Step 2 was to use eye tracking to RLTS an ad. This analysis revealed big differences in the attention given to viewable advertising between desktop, mobile and OOH. 
On desktop, if an ad is served in a viewable position, consumers have a 22% chance of noticing the ad – meaning that they had at least one eye fixation on the ad.  For mobile, larger format ads, such as DMPUs (300x600) take up almost the whole of the screen, and are far more likely to get noticed than the smaller and more ubiquitous 320x50 formats.  For OOH, digital panels are more likely to get noticed than their static counterparts, especially in faster moving environments.

This data makes Mobile and OOH advertising look considerably better than desktop display advertising. The size and salience of OOH, and quasi-sequential nature of some mobile advertising mean that viewable advertising in both these media are more likely to gain attention than desktop display.

Visibility Adjusted Contacts (VACs)

The third challenge was to apply the VAC criteria across all media: the percentage of all ads served that are actually seen i.e. Viewability Rates multiplied by Likelihood to See. According to this overall statistic, OOH almost always beats mobile and desktop. As we have seen, desktop tends to have quite good Viewability rates, but those viewable ads are often ignored. Meanwhile, mobile is the other way around; once viewable, mobile ads are quite good at being seen, but they are limited in their impact by relatively poor Viewability.

Dwell Time

Most advertisers would be disappointed if their advertising only received a single eye fixation so it was important to identify the average dwell time with ads across different media. Here, the surprising thing is not the difference but the consistency across media; average dwell times of different media and formats are almost always somewhere between 1 and 2 seconds. Interestingly, dwell times for OOH are often higher than desktop and mobile, especially for pedestrians and larger formats.

Short and Long Attention Media

Although OOH is often regarded as the medium with the shortest attention span, it appears that dwell time is similar across the board, with OOH actually getting the longest time of the three media.
However, we should not exaggerate these findings. The key point to take away is this: OOH is indeed a ‘short attention’ medium, but so are mobile and desktop display. Much can be achieved in a short amount of time.
Data from Lumen and others suggests that 2 seconds attention is plenty of time to deliver powerful brand messaging and build brand recall. These dwell time findings indicate that online advertising could equally take a leaf out of decades of OOH creative best practices and apply them to online.

The Future for Media is a Common Currency of Attention

Agencies have long held OOH advertising to a higher standard than other media; OOH ads not only have to be viewable, they must be viewed to count as a contact. This is a rigorous standard, but a necessary one. The media industry is now able to apply the same rigorous standards of measurement to other media. Scalable, low cost eye tracking of the type pioneered by Lumen allows media buyers to go beyond measuring what people could see to calculate what people actually see, across a wide variety of media. The results offer a possibility to establish a common currency of attention; a stable and consistent yardstick with which to measure all media. Agencies often say that they are interested in ‘buying eyeballs’. Up until now, Opportunity to See has been the proxy metric for this goal. However, with eye tracking we are now able to look beyond potentialities, and focus on what really matters - Attention.