NYSE Composite Index - 2015

The following graph plots the year-to-date performance of the index for 2015 compared to the probability calculated by a random walk model.

Initial Value: 10839.2 Hist. Volatility: 0.63% Annual Drift: 7% Final Value: 10143.4 Percentile: 12%
Click on the image for the high resolution version.

The high to date and low to date prices of the stock plotted against a random walk model for 2015 (what's this?).