Young people have always perplexed their elders. Today’s youngsters are no different; indeed, they are baffling. They have thin wallets and expensive tastes. They prize convenience and a social conscience. They want their shopping to be at once seamless and personal. They crave authenticity while being constantly immersed in an ersatz digital world. As these youngsters start spending in earnest, brands are trying to understand what these walking paradoxes want and how they shop. The answers will define the next era of consumerism. Their absolute numbers are formidable. The European Union is home to nearly 125m people between the ages...