Have you ever noticed how, in many cities, when it starts to rain, people magically appear with a whole lot of umbrellas for sale? They don’t seem to come from any particular place, and as soon as the rain disappears, so do they. I’ve always wondered where these people come from, and how it is they always happen to have an inventory of umbrellas for sale stashed somewhere nearby, just in case it rains. I’ve experienced this phenomenon in San Francisco, New York, Chicago, and even Rome – where I was once caught in a surprise downpour and actually bought an umbrella… for a mere € 2! It continues to…