In a study of display advertising platforms, including Google and DoubleClick, we discovered five factors that affect the viewability of an ad, or how likely the ad is to be seen, and we’ve highlighted them in this infographic.

Source: www.thinkwithgoogle.com

An ad served doesn’t necessarily equal an ad viewed, and digital advertisers and publishers are catching onto this as the industry shifts toward valuing viewable rather than served impressions. So what affects an ad’s viewability?

1. Viewability varies significantly by page position and ad size
2. Page position doesn’t tell the whole story. 
3. Vertical ad units are the most likely to be seen by users.
4. On average, publishers have 50% viewability rates, but some publishers have much lower viewability.
5. Consider targeting sites with more engaging content to achieve higher viewability rates.

See the full study at:

http://think.storage.googleapis.com/docs/the-importance-of-being-seen_study.pdf