What is the definition of current efficiency?
The theoretical definition is the ratio of electrons used to make the useful product out of the total electrons that were supplied. The problem in the chemistry literature with efficiency definitions, however, is that you will more than likely find that different people will use different definitions for one reason or another (easier to calculate, some type of comparison in their work, or simply because it sounds or looks better). The right way to deal with efficiencies, then, would be to define how the efficiency is calculated in order for the reader to know what you are talking about. If this is an academic setting, I would stick to the theoretical definition, but ask your professor as to what their favorite definition would be.