it is difficult to find two assets that are uncorrelated, and it is practically impossible to find three. It is absolutely impossible to find more than three mutually uncorrelated assets. The reason for this is simple. A portfolio of two assets has only one correlation. Three assets have three correlations, and four assets have six correlations. (This is the same reason why big offices have messier politics than small ones. A three-person office has three interpersonal relationships; a 10-person office has 45 relationships.)
