"[T]he lion’s share of the company’s [Alphabet's] revenue still stems from the core Google segment and its advertising business in particular. Ad revenue amounted to $22.67 billion in the three months ending June 30, accounting for 87 percent of the company’s total revenue. Google’s advertising business is safely on track to surpass $90 billion this year, making it the largest ad-selling company in the world by far. "--Statista.com
Net digital ad revenues of Google as percentage of total digital advertising revenues worldwide from 2016 and projected through 2019 are in the range of 32-33%. Competitors to Google are Amazon (in both search and advertising) and Facebook (in advertising). See also Google and Facebook Are the New Media Barons | Bloomberg.com.
|Change in advertising revenue, 2010-2016. Source: Magna Global, Bloomberg Intelligence and Google filings.|
|source: $GOOGL / $GOOG Q2 2017 Earnings Release|