1. A method for partitioning a plurality of investments into groups, implemented by a computer coupled to a database of investment data, the computer being programmed to perform the method steps, comprising: calculating by the computer, as similarity values, a measurement of similarity related to investment characteristics between investments in every possible pair of investments from among the plurality of investments; performing by the computer a mathematical conversion on the similarity values, such that the similarity values are mapped, as mapped values, into a range of positive values in which a lower positive value reflects a greater degree of similarity between investments in an investment pair; and partitioning by the computer the plurality of investments into groups such that a sum across all the groups of the mapped values between each pair of investments within each group is minimized, the sum increasing when any investment from a group to which it has been assigned is moved to any other group.