In this paper the condition of a "statistically homogeneous" suspension is carefully analyzed. This condition requires that in the presence of a macroscopic gradient of the electric potential there are no macroscopic ion concentration gradients in the system. It is shown that the use of this condition, which should always be required in the calculation of the electrical conductivity of colloidal suspensions, is far from trivial. Furthermore, its hasty use can lead to substantial errors in the calculation of the conductivity increment.