These are some of my notes from the book “The Success Equation” by Michael Mauboussin. This book was spotted on Warren Buffett’s desk in this tour of his office. There’s lots more interesting stuff in the book, but these notes in particular answer the question “How do you separate luck and skill?” We’ll start off with some definitions:
Luck is a chance occurrence that affects a person or a group (e.g., a sports team or a company). Luck can be good or bad. Furthermore, if it is reasonable to assume that another outcome was possible, then a certain amount of luck is involved. In this sense, luck is out of one’s control and unpredictable. Randomness and luck are related, but there is a useful distinction between the two. You can think of randomness as operating at the level of a system and luck operating at the level of the individual. Luck is a residual: it’s what is left over after you’ve subtracted skill from an outcome.
The definition of skill depends on how much luck there is in the activity. In activities allowing little luck, you acquire skill through practice of physical or cognitive tasks. In activities incorporating a large dose of luck, skill is best defined as a process of making decisions. Here, a good process will have a good outcome but only over time. Patience, persistence, and resilience are all elements of skill.
Separating luck and skill
At the heart of making this distinction lays the issue of feedback. On the skill side, feedback is clear and accurate, because there is a close relationship between cause and effect. Feedback on the luck side is often misleading because cause and effect are poorly correlated in the short run.
In most cases, characterizing what’s going on at the extremes is not too hard. As an example, you can’t predict the outcome of a specific fair coin toss or payoff from a slot machine. They are entirely dependent on chance. On the other hand, the fastest swimmer will almost always win the race. The outcome is determined by skill, with luck playing only a vanishingly small role.