The current efficiency eta for the transport of ions through an ion-exchange membrane is analyzed theoretically. In particular, the effect of discretizing the fixed charges contained in the membrane into charged intervals on eta is investigated. We show that if the applied current density I is low, a membrane with a continuous linear fixed charge distribution has a higher eta than a membrane with evenly distributed charged intervals, and the larger the number of charged intervals the lower the eta. If I is high, a membrane with randomly distributed charged intervals may have a higher eta than that of a membrane with a continuous linear fixed charge distribution. It can be inferred that, as far as raising eta is concerned, distributing fixed charges discretely and/or randomly in a membrane has no practical advantage.