Silicon Valley internet giants Google and Facebook have raked in over $100 billion in global advertising spending, a recent report says. The two companies have grown their share of global ad revenue from about a tenth in 2012 to a fifth in 2016, according to an annual ranking presented by data and analysis agency Zenith. Last year, Google and Facebook reached $79.4 billion and $26.9 billion in advertising revenues respectively. They were followed by US-based telecoms firm Comcast, which brought in $12.9 billion. According to the agency, online advertising has overtaken television to become the world's largest ad medium. "Digital platforms that are funded by internet advertising dominate our top 30 ranking. As well as [Google parent company] Alphabet and Facebook, there are five more pure-internet media owners in the top 30: Baidu, Microsoft, Yahoo, Verizon and Twitter," the report says. The seven online platforms generated $132.8 billion in internet advertising revenue last year – 73