Google's search ad dominance is massive but shrinking slightly

Google is expected to net more than 71% of the U.S. search advertising spending this year, down from roughly 74.7% of market share in 2017, per eMarketer.

Why it matters: Google relies on search advertising for the majority of its revenue. The Department of Justice's antitrust lawsuit over its dominance of search threatens the core of its business.

Be smart: Over the past few years, Amazon has slowly started to give Google a run for its money in search advertising.

• By 2021, it's expected to control nearly 16% of the search ad market, up from 6.5% in 2017.
• Still, Amazon's search ad business can only really grow in line with its ecommerce business, as most of the search ads bought on its platform are purchased by marketers trying to boost their products in search results on Amazon.com. And Google is pushing hard to compete with Amazon and other platforms in shopping.

Yes, but: The picture isn't so rosy for Google. This year, it is expected to see its first advertising declines year-over-year in over a decade, due in large part to declines in ad spending by the embattled travel industry during the COVID-19 pandemic.