At $100 billion, Google’s travel business contributes about 15 percent to Google’s $650 billion market cap. For the first six months of 2017, Priceline’s performance-advertising spend was up 23.5 percent compared with the year-earlier period. Expedia does not disclose quarterly ad spend specifically, but direct marketing costs increased 28 percent, and that would be a good approximation of its growth rate. This suggests that 2017 digital ad spend for Priceline is on pace for $4.3 billion, and Expedia for $2.9 billion. Running through a comparable growth path for Airbnb; metasearch engines such as Kayak and Trivago, and suppliers, including hotels and airlines, 2017 travel spend on Google will likely jump 25 percent, generating close to $14 billion in revenue for Google. For context, Google revenue as a whole has grown 23 percent in constant currency during the first two quarters of the year. Get the full story at Skift