> adblocker | either AdBlock Plus (ABP) or uBlock Origin, the two most popular ad-blocking Firefox add-ons Adblock Plus ("ABP") does not block a lot of ads by

> adblocker | either AdBlock Plus (ABP) or uBlock Origin, the two most popular ad-blocking Firefox add-ons Adblock Plus ("ABP") does not block a lot of ads by default, as ABP's "Acceptable ads" is opt-out -- i.e. it is enabled by default. I wonder if this was taken into account, and if not surely this affected the result of measuring "the effect of ad blocking on user engagement with the web", as you can't categorize ABP's "acceptable ads" as "ad blocking".