The Chunin Selection Exams (中忍選抜試験, Chūnin Senbatsu Shiken) are an opportunity for genin to be promoted to chūnin. The exam structure and evaluation processes differ from one exam to the next so that genin cannot come prepared. Villages originally held their own individual exams. Following the Third Shinobi World War, exams that are open to all villages started being held bi-annually, with villages taking turns for hosting responsibilities. These shared exams improve relations between the villages, present up-and-coming ninja to clients, and create an opportunity for gambling.
Although the exams, specifically the final round matches, are designed for there to be an ultimate "winner", success does not guarantee promotion nor does failure preclude it; if the observing ninja and daimyō feel a genin displays the necessary qualities for a chūnin, that genin will be promoted regardless of how they place in the exams. For this reason it is possible for as many as all of the finalists to pass, or even for none of them to. Being victorious simply expands the participant's chances of demonstrating their qualities in the next match.
Having too many participants to advance to the next stages seems to be an undesired result, as the examiners tend to run additional preliminaries to reduce the number of finalists.