Data from Pixalate show that click fraud is prevalent online. During the first half of 2017, as many as three in four clicks on programmatically purchased 300 x 600 ‘half page’ desktop ads (a unit Google describes as one of the fastest growing sizes) are fraudulent. The average across all formats is one in three (32%).

Data show that click fraud reduces with screen size. Of all measured clicks on the smallest ad (320 x 50) on the smallest screen (mobile), only 7.2% were fraudulent. This was ten times lower than the rate for the largest ad on the largest screen, a 300 x 600 desktop half page (75.6%).

Generally, the greater the physical area, the higher the rate of click fraud. This trend is true within the particular screen size only; for example, an ad with a total area of 153,600 pixels on a mobile (i.e. 480 x 320) is half as likely to receive fraudulent clicks than a desktop ad of only 65,520 pixels (i.e. 728 x 90), despite being over twice the physical area.

There are exceptions to the rule. Despite being the smallest desktop ad by physical area, the 728 x 90 ‘leaderboard’ format recorded the second-highest click fraud rate (57%) among desktop units, suggesting ad placement is also a factor.

This Data Point was drawn from March's Global Ad Trends report, which focuses on threats to the digital advertising ecosystem.