How are companies using our personal data? It’s a familiar concern. Online retailers are tracking us so they can sell things to us. Bricks and mortar retailers have loyalty card schemes. Our banks and credit card companies know all about us. And of course, the big computer and telecoms companies could potentially track our internet searches, our phone calls – even our location as we wander around. But this isn’t the first time that large corporations have gathered sensitive data about their customers. We tell the shadowy story of how the personal details of Americans were pooled among insurance companies more than a hundred years ago.