The turkey leftovers are long gone and the holiday shopping season is moving into crunch mode. And though Thanksgiving-weekend retail sales were a little disappointing, I’m more intrigued by—and upbeat about—an emerging, high-tech aspect of this annual winter spending orgy: the smart use of big data.

With more purchases happening digitally today, big-data analytics has become a crucial but often little-understood link between the shopper and the retailer, both around the holidays and year-round. The technology is providing shoppers better selection, customer service and more targeted advertising, while helping retailers sell more of those big TVs and hot handbags you want under the tree.

E-commerce providers can now leverage algorithms to target sales and promotions to the groups most likely to buy; they can also promote items that complement specific products a shopper has already purchased, like throw pillows to go with a couch, or jewelry to match a just-purchased dress. Big data has even helped retailers tweak the timing and frequency of their emails to customers. (Guess what: Lots of people read emails from retailers at lunchtime.) These communications are also highly personalized. One flash-sales site I know can send out tens of thousands of variations of its daily email, based on your preferences and past shopping history. Read more.