Expedia Group, the umbrella over Brand Expedia, Hotels.com and others, accounted for the highest amount at $5.68 billion. Booking Holdings, owner of Booking.com, OpenTable and Kayak, came in at $4.96 billion.

This marked an increase of 8% by the two organizations on their marketing activity in 2017, when they collectively spent some $9.8 billion.

But murmurings of discontent among the companies about how much they spend with Google have surfaced in recent years, as they see how the brand that helps them get customers is working harder each year to effectively compete against them.