Amazon.com’s advertising business “has been quietly growing into a massive driver of current and future profitability,” Piper Jaffray analyst Michael Olson tells investors in a research note. The analyst estimates that in 2018, Amazon advertising revenue will be around $8B, potentially contributing greater than $3B to operating profit. By 2020, he expects Amazon ad revenue of $16B and by 2021, he believes it is highly likely that profits contributed from advertising will exceed those from Amazon Web Services. Applying an advertising comp multiple of 16 times to estimated 2020 Amazon advertising operating income suggests an ad business that should be valued at $150B-$190B, Olson contends. As such, he believes investors “should be focused on Amazon advertising now.” The analyst reiterates an Overweight rating on Amazon shares with a $2,100 price target. The stock closed Friday down $12.22 to $1,886.30.