NYSE Composite Index - 1990

The following graph plots the year-to-date performance of the index for 1990 compared to the probability calculated by a random walk model.

Initial Value: 2062.3 Hist. Volatility: 0.63% Annual Drift: 7% Final Value: 1908.45 Percentile: 11%
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 1990 (what's this?).