National production shares may be a relevant measure for strategic raw materials in view of the frequent government involvement in such markets. Viewed this way, uranium production is exceedingly concentrated, with four countries accounting for 90 per cent of the global total. Though national concentration is particularly important for uranium, in view of the profound governmental intervention and control in the production and trade of this commodity it is also important to study concentration among corporate decision units. Transparency of transaction terms is of course greatest in cases where transactions are centred on an exchange like the LME which regularly publishes price and turnover figures. Empirical observation of successful supply collusion suggests that substantive market action is usually preceded by an extended period of general collaboration among suppliers, on issues not directly related to profit. The existence of international cartel arrangements in the uranium market between 1972 and 1975 has been clearly admitted.