As for the market leaders, eMarketer expects Alphabet 's ( GOOG -1.33% ) ( GOOGL -1.33% ) Google and Facebook ( META -0.40% ) to control 37.1% and 20.6% of the entire market, respectively, this year. But by 2020, the firm expects Amazon's share to grow to 7% as Google and Facebook's combined share slips from 57.7% to 55.9%.