The Importance of Viewability for CTR
The Image Chapter
At Neon, we are driven by the curiosity to understand how people interact with images. We’re also driven by our math and science backgrounds to understand these interactions in a thorough and data-driven way. One of the ways we approach this curiosity is by using metrics like click-through rate (CTR) to understand image and video thumbnail performance online.
Why is CTR for images important?
For any visual content, CTR is an important metric because it gives a direct measure of how much an image is resonating with its audience. Early on, we measured CTR as the simple ratio between image clicks and image loads. We soon realized that the CTR calculated in this way was misleading — many of our customers’ web pages had images hidden in carousels, in drop-down menus, or, most commonly, “below the fold”. These non-visible images were being factored into our CTR calculations.
What is viewability?
The IAB (Interactive Advertising Bureau) and MRC (Media Research Center) define a viewable ad impression as one that’s at least 50% visible for at least one second. For Neon’s purposes, this viewability standard is extended beyond ads to include any image visible on the page.
Unlike static banner ads, video thumbnails or images associated with an article tend to not be fixed at a certain location on the page. More often than not, with the influx of newer content the images and other content get rearranged on the page and often go below the fold, making them “invisible” to the user unless she scrolls down. If CTR measurement were based purely on loads, then we’d expect to see a sharp decline in CTR on this image that has now moved below the fold, because fewer people scroll down far enough on the page to have a chance to click on the image. The graph below illustrates this with a real world example from one of our customers. There is a sharp decline in the number of times the image is actually seen by the user once the image goes below the fold.
The ad industry has begun to recognize the importance of viewability and is moving quickly towards adopting standardized viewability metrics for banner and video ads. The effects of this shift can be seen almost anywhere you turn: for example, ESPN recently relaunched their website to enhance ad viewability.
Given this industry-wide push, all signs point to the importance of factoring viewability into video thumbnail and image engagement metrics.
Can we use a better metric for viewability?
CTR measured as the ratio of clicks to image views (instead of image loads) is what we call True CTR. Often, load-based CTR and True (or view-based) CTR for the same images are very different. With our customers, we usually see that the True CTR is much higher than the load-based one, which you can see in the graph below. Major factors influencing this include the “below the fold” effect as well as images hidden in carousels and drop down menus as I mentioned above. True CTR gives a more realistic idea of how users are actually interacting with content, so Neon uses True CTR when calculating engagement for our customers.
For further reading, check out VentureBeat’s post on viewability standards or RTB Insider’s post on viewability measurement.
