Comparison of company revenues with data in WARC’s Adspend Database shows that the duopoly of Google and Facebook accounted for approximately 63.8% of all online advertising expenditure in 2017, up from 57.5% in 2016 and 47.1% in 2012.

The latest quarterly reports, published today, show that the $135.3bn in combined revenue equated to a quarter of all media spend worldwide in 2017, up from a fifth in 2016 and just 9.4% in 2012.