More than 1-in-5 consumers purchased or browsed for products online via a mobile device when holiday shopping for themselves or others, according to global information company The NPD Group. That number was double among Millennial consumers, between the ages of 18 and 34. “Online shopping continues to grow in importance, and Holiday 2015 was a clear example of this, with mobile playing a key role,” said Marshal Cohen, chief industry analyst, The NPD Group, Inc. “Consumers, especially the youn...