1. A computer system for calculating a score for a separately accountable business unit, the computer system comprising: a program memory storing code for controlling a processor; a score memory storing the score for the separately accountable business unit, the score being indicative of impact on the environment as a consequence of the economic activities of the separately accountable business unit; and a processor connected to the program memory for reading and being controlled by the code; wherein the program memory stores: accessing code for controlling the processor to access financial account data indicative of recognized costs for the separately accountable business unit; financial account processing code for controlling the processor to process the financial account data by adding external environmental costs to the recognized costs to calculate the score for the separately accountable business unit using the processed financial account data, and to store the calculated score in the score memory, wherein the external environmental costs comprise costs required to preserve the environment as a consequence of the economic activities of the separately accountable business unit; and supplier score accessing code for accessing scores indicative of environmental impact for suppliers of at least one of goods and services to the separately accountable business unit; wherein said supplier score accessing code includes supplier account data, and supplier score determining code for determining scores for the suppliers using the account data and environmental information, and said financial account processing code is adapted to process the account data using scores accessed for the suppliers.