The IAB conducted a study on the digital ad industry and found that there is approximate $8.2 billion lost each year to a combination of fraudulent impressions, infringed content, and "malvertising". Fraudulent impressions make up the biggest chunk of that lost revenue with an estimated $4 billion lost due to non-human impressions generated on ads. The infringed content makes up about $2.4 billion of lost revenues and stems from video programming, music, and other content being illegally distributed online. Malvertising sees a large chunk of lost revenue as well with the majority of that being lost due to ad blocking. The full report done by the IAB can be viewed here.