The Performance Index Graph shows the distribution of performance indices for each runner over all the legs of the course using a density curve. A runner's performance index on a leg is defined as the average of the fastest 25% split times on that leg divided by the runner's split time. The curve is highest at the x-values that correspond to the range into which the largest number of the runner's leg places fell. Each leg contributes height in the y-direction proportional to its length. A curve with a high, narrow peak and without other, outlying peaks shows that the runner's performance indices were consistent during the entire course. A more spread-out curve with several peaks indicates more erratic performance indices.