Rolf Schroemgens, co-founder and chief executive officer of Trivago GmbH, smiles during an interview at the Nasdaq MarketSite during the company’s initial public offering (IPO) in New York, U.S., on Friday, Dec. 16, 2016. Trivago, the German-based travel site majority-owned by Expedia Inc., climbed in its debut after the company priced its U.S. initial public offering below the marketed range. Photographer: Michael Nagle/Bloomberg via Getty Images