Google’s revenue growth trajectory at well over 20 percent in the fourth quarter, as disclosed Thursday, suggests that we should expect to see digital advertising remain an area of modest operating deleverage for the online travel agencies. This means that advertising spending grows faster than revenue and leads to margins decreasing. The caveat would be if the online travel agencies have been able to improve return on investment from each ad dollar spent, then we could see revenue outpace advertising spend once again. Our base assumption is that advertising spending continues to modestly outpace revenue growth for Priceline and Expedia, but other operational cost line-items would counteract the advertising margin impact where operating expenses increase slower than revenue growth given scale efficiencies. Get the full story at Skift Read also "Google’s mobile search revenue grows, suggests higher mobile ad rates ahead"