The growing US search ad market is dominated by Google. But Amazon and smaller players have the ad giant in their crosshairs. According to our latest US ad spending forecast, Google’s share of search ad revenues will drop, while that of Amazon will grow over the next two years.

The US search ad market overall will grow nearly 18% this year to reach $55.17 billion. Google will obtain a 73.1% share, translating to $40.33 billion. But, while Google will remain the dominant player for the next several years, its share is dropping. By 2021, it will capture 70.5% of the market.