Correlation is a measure of the interdependence or strength of the relationship between two investments. It tells us something about the degree to which the variations of returns from their respective means move together. So if two investments are positively correlated, when one performs above its mean return it is likely that the other will also perform above its own mean return. If two investments are negatively correlated, when one performs above its mean return it is likely that the other will perform below its mean return. Note that correlation says nothing about the mean returns themselves – they could both be up, or both down, or one could be up and one down. To measure the strength of the relationship, we use the correlation coefficient. Values range from –1 (perfect negative correlation), through 0 (no correlation or uncorrelated) to +1 (perfect positive correlation). From a risk management perspective, it is generally favorable if two investments are uncorrelated because it means that there is no identifiable directional pattern or proportional relationship between the deviations of their monthly returns from each of their respective trends – sometimes investment B is positively correlated to investment A when the returns of A are positive and negatively correlated when they are negative, meaning that over a period of time our strategy returns get closer to non–correlation. This produces a smoother overall return profile.