Big, cheesy grins — simple, really. In response to last week’s Ralph Lauren handbag thief, the author of The Steal: A Cultural History of Shoplifting shares suggestions in the Post for reducing shoplifting at boutiques too classy for visible security: “While it might seem absurd that smiling at a thief stops them from stealing, it turns out that people often shoplift out of rage or a sense of injustice. A smiling face can disarm them; it also shows that someone is paying attention. Perhaps the [Ralph Lauren] purse stealer is one of the small percentage of professional shoplifters. Or maybe they just had a sour salesperson.” So when you’re smiling (keep on smiling), the whole world smiles with you … and no one steals your $20K bags.