I've been thinking a lot recently about the mistakes I make in predicting things. Often I will just observe a trend, and then extrapolate that trend into the future. This will be my prediction. The world doesn't work like that though. Trends will last for a while, but then something changes, and before you know it the world has changed direction. I want to think more about how and why a current trend could change direction. For example - what would it take for the trend of rising property prices in London to change direction?