Loading the player... Covariance is a measure of the degree to which returns on two risky assets move in tandem. A positive covariance means that asset returns move together, while a negative covariance means returns move inversely.
1. Rotterdam (the Netherlands) This Dutch harbor was the largest in the world, until Shanghai and Singapore grew even larger in 1986. This satellite photo gives an indication of the size of the Port of Rotterdam. (Image via Mannlines) About an hour and a half to the south of Rotterdam is Antwerp, the largest port in Belgium.
1 The largest lake in the world by area is the Caspian Sea, with 394,299 kmÂ². The largest freshwater lake by area is Lake Superior (82,414 kmÂ²), part of the Great Lakes of North America.  The longest freshwater lake is Lake Tanganyika, with a length of about 660 km.