A novel criterion for digital synchronous communication efficiency estimation is defined. All attributes such as bit error probability, coding efficiency, initial synchronization time, efficiency of detection of timing anomalies and sync recovery, reliability of the lock indication, and the amount of redundancy insertion in the data stream for synchronization and error-correcting coding purposes are included in a single parameter called system The expression for this parameter is derived under the assumption of signal ergodicity and steady-state operation. In its final form, this parameter seems obvious almost by inspection. Even so, until now, it has not been used in the analysis of communication efficiency. The analysis of this parameter for several different systems is presented as an illustration.