Google lost out on $6.6bn (£4.2bn) of revenues to ad blockers in 2014, according to a report from anti-adblock tech firm Pagefair.

This figure is based on a 10 per cent adoption of ad blocker software in the US – which Pagefair says is a conservative estimate, with the real figure closer to 14 per cent. For the rest of the world, its slightly more complicated.

“The actual global adblocking rate is probably about five per cent, while the percentage of adblocked dollars is much higher,” Pagefair CEO and co-founder Sean Blanchfield told Mobile Marketing. “There is very low adblocking among many non-western countries, where access is primarily mobile, but where the ad spend is lower.”

Weighted by ad spend in each market, Pagefair believes that adblockers in non-US markets – where adoption can be as high as 35 per cent in some Northern European countries – contribute to a overall average drop of 17.5 per cent in ad spend.

Thats a fairly stunning figure but, according to the report, it would be even higher – $10bn globally – if not for Googles whitelisting deal with Adblock Plus to exclude its search ads from the filter. This deal reportedly saw Google forking out $25m to Eyeo, owner of Adblock Plus, but the study suggests it saved $3.5bn last year as a result.

Hardest hit by adblockers are Googles Adsense and Doubleclick display businesses, which together lost $2.1bn globally in 2014 – around one-sixth of their $12.5bn revenues over the period.

Due to its pre-roll ads being blocked, YouTube reportedly lost out on $675m.