Correlation is a measure of the extent to which two random variables track one another.
The correlation of two random variables can range from -1 to 1.

Our system measures the correlation of a stock relative to its national index.
When a stock is positively correlated to its national index, it tends to appreciate or depreciate at the same time as its index. When a stock is negatively correlated to its national index, it tends to fall when its national index rises, and vice versa.

Example: on October 16, 2002, UBS has a correlation of 0.92.
This means that UBS is highly correlated to the SMI and tends to follow 92% of its up and down movements.