NYSE Composite Index - 2012

The following graph plots the year-to-date performance of the index for 2012 compared to the probability calculated by a random walk model.

Initial Value: 7477.03 Hist. Volatility: 1.41% Annual Drift: 7% Final Value: 8443.51 Percentile: 64%
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 2012 (what's this?).