Mankind has learned to collect, process and use huge amounts of data in science, business and everyday life. But what to do with the data we don't have? Is it acceptable to ignore what we do not notice? British statistician David Hand believes that this is at least short-sighted, and sometimes extremely dangerous. In his book, he identifies 15 types of data that influence our decisions and actions that remain in the shadows. For example, counting the distress calls people in poor areas might have made if they had smartphones, medical research results that were deliberately withheld or inadvertently distorted, or data that became obscure due to a poor set of inclusion criteria. to the sample. Hand also talks about what measures can mitigate the effect of dark data and how they can be turned to your advantage.