S&P 500 - 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: 2058.9 Hist. Volatility: 0.58% Annual Drift: 7% Final Value: 2043.94 Percentile: 27%
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?).