“Stories are powerful and memorable. That is why I have told so many in this book. But an individual anecdote can only serve as an illustration. To really convince yourself, much less others, we need to change the way we do things: we need data, and lots of it. [...] People become overconfident because they never bother to document their past track record of wrong predictions, and then they make things worse by falling victim to the dreaded confirmation bias - they only look for evidence that confirms their preconceived hypotheses. The only protection against overconfidence is to systematically collect data, especially data that can prove you wrong. [...] "If you don't write it down, it doesn't exist". In addition, most organizations have an urgent need to learn how to learn, and then commit to this learning in order to accumulate knowledge over time. At the very least this means trying new things and keeping track of what happens. Even better would be to run actual experiments. [...] The ideal organizational environment encourages everyone to observe, collect data, and speak up.”