If you have ever been involved in preparing and implementing projects, you know one golden rule: something will definitely go wrong. This is especially true in financial matters when you draw up your budget, but as a result of a series of unpredictable factors, you end up with completely different numbers. And not to mention when you repeatedly have to postpone the deadline due to the project's large scale.

You never know where and when disaster will strike. 99.5 percent of large projects do not meet the initial budget and time promises for various reasons. Perhaps you’ve heard of the bridges and tunnel across the Great Belt in Denmark — an incredibly large infrastructure project that significantly exceeded its budget. Bent Flyvbjerg, one of the authors of this book, later found that the officially stated 29 percent cost overrun was heavily underestimated. In fact, the overrun was 55 percent for the whole project, and for the tunnel alone, it’s estimated as much as 120 percent.

What about the Olympic Games in Montreal, which exceeded the budget by 720 percent, or the Scottish Parliament, which, when it opened in 2004, exceeded the budget by nearly an unimaginable 978 percent? All these situations were unpredictable. None of the organizers thought it could happen. In addition, the project's expected benefits turned out to be much smaller than assumed.

Bent Flyvbjerg even came up with an ironic “Iron Law of Megaprojects.” The gist is that when carrying out these projects, one will almost always go over budget, over time, and under benefits. And this, unfortunately, happens so often that it’s not even funny.

Flyvbjerg’s study, which analyzed 258 transport projects, once again confirmed this law. On average, railway projects had a cost overrun of 45 percent. But it wasn’t just transport that suffered from this pattern of poor management, which ultimately ruined projects. Any large-scale project in any country or region — whether an IT project or a cultural event — was a potential victim of inaccurate forecasting and poor management.

What conclusion should you draw from this right now, even if you’re not yet planning to organize the Olympic Games or build a parliament? You must understand that even the smallest and seemingly unambitious project can face disasters. You must treat projects as systems, which are influenced by other complex systems, like climate change or fluctuations in the job market. This way, you consider all unpredictable situations with your project.