The secret to showing appreciation is that scarcity matters. It should involve effort: a handwritten note is better than an email, which is better than an algorithm. It should feel personal, not part of a scheme cooked up by the human-resources department. And it should be sufficiently rare to register as meaningful; thanking everyone for everything turns gratitude into a commodity. In other words, appreciation is not a big-data project. Individual managers can harness the power of small gestures to make a real difference to their teams.