NYSE Composite Index - 1974

The following graph plots the year-to-date performance of the index for 1974 compared to the probability calculated by a random walk model.

Initial Value: 547.93 Hist. Volatility: 0.99% Annual Drift: 7% Final Value: 382.03 Percentile: 4%
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 1974 (what's this?).