1.
Introduction
What would it be like if you knew in advance what was going to appen? For ages people have been trying to predict events. For instance, h where the most fertile soils can be found or what tomorrow will be like. Just consider the weather, for example. Wouldn’t it be great to know in advance that the weather will be nice later in the week, so you could plan a weekend away and not have to worry about showers or thunderstorms? Predictions enable you to take into account what you think will happen in the future, such as earthquakes, changes on the stock market or the showers I mentioned earlier. You can sometimes make predictions because of the existence of a degree of regularity or because ‘phenomena’ can be incorporated into mathematical models. For instance, we know precisely when the next eclipse of the sun will take place. Sometimes, however, It is difficult, particularly when you know very little about a topic. Predictions can help us to see the possible consequences or results of our own activities or the activities of others. They provide an image of a moment in the future. Anticipating like this can increase your chance of success. Success in the form of a longer life, making fewer errors or making the right assessments. The trouble people will go to in order to obtain a good prediction depends on the added value of what is being predicted. Consider, for example, predictions on share prices. This is enormously complex, but because of the large potential margin for profit, millions are invested in order to obtain insight in developments in the value of shares and bonds. How safe would we be if the police knew everything in advance and could prevent all forms of crime? Society would be completely different. This book is about a complex form of prediction: predictive policing, or in simple terms: police work based on predictions. Is it possible to predict crime? Can crime be recognised at an early stage? What are effective