While pondering the definition of efficient, as a Factor that Causes Influence one might stumble across it's sister word - sufficient.
If Efficient refers to being effective without wasting time, effort or expense; and Sufficient is fulfilling a need or requirement without being abundant - when is it efficient to be sufficient?
A comparable I have often referred to is the difference between having an efficient engine that uses less gas vs. sufficient gas to travel to a destination. The two definitions are miles apart!
Clarification may be obtained by exploring efficient business models and their practices: Mr. Lube; McDonald's, FedEx, Tim Horton's.
Which business do you deal with on a regular basis due to their efficiencies - the experience is enjoyable - and which business would you avoid if given a competitive option, due to their focus on sufficiencies: Airlines, Bureaucracies, and Monopolies. (names have been withheld to protect the innocent)
It seems the new model for many international airlines is to provide sufficient service, so please, leave your baggage at home!
In dealing with the public, your family, friends and your clients - would your behaviour be classified as Sufficient, or Efficient?