Self-attribution bias
Crediting good outcomes to one's own skill and bad ones to outside circumstances: two different measures for results of the same nature.
How to read the number
The direct consequence is larger positions after a run of wins: the experience feels like confirmation of a method while it confirms only a favourable stretch.
When the metric lies
The bias strengthens with experience, because a longer record accumulates more wins. Skill can be separated from the market only by comparison with a benchmark over the same period, never by feel.
Also known as: self-serving attribution