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Effectiveness Versus Efficiency

Effectiveness and efficiency act against one another, and may be key drivers in design.


Working definitions

  • Efficiency: The rate at which a system produces useful output as a percentage of all inputs.
  • Effectiveness: The capacity of a system to achieve its objectives.

Notes on "effectiveness"

The definition of effectiveness is weak. We need a better definition. Some alternatives include:

  • the quality of being able to bring about an effect, and causing an effect. (Wordnet)
  • the extent to which a specific intervention, when used under ordinary circumstances, does what it is intended to do. (US Dept of Veteran Affairs)
  • The degree to which program or system objectives are being achieved. (Quality Assurance Project)
  • Ability to achieve stated goals or objectives, judged in terms of both output and impact. (US EPA)
  • A measure of whether the Objectives of a Process, Service or Activity have been achieved. (Information Security Management Maturity Model)

Some of the definitions indicate that effectiveness is a quality, not a quantity. Clearly, there is no standard measure of effectiveness (as there is for efficiency).

:!: HERE ⇒ What is known about measuring effectiveness?

There's a difference (in medicine) between efficacy and effectiveness. Per 1, efficacy refers to how well an intervention works in subjects who receive it, whereas effectiveness refers to the evaluation of an intervention in subjects to whom the intervention is offered. The difference between efficacy trials and effectiveness trials is compliance.

In [AEO11]: “…the nature of [ecology] is often misunderstood. Simply maximizing efficiency in the use of resources is helpful in the short term but ultimately ineffective where a resource is finite and non-renewable. The resource will eventually run out and no amount of efficiency will sustain effectiveness.

Balancing effectiveness and efficiency

Typically, systems are optimized for efficiency without (properly) considering effectiveness. There is significant evidence for this in the literature.

  • [VS10] clearly defines efficiency as the subject of optimization, and doesn't mention effectiveness at all. Yet the problems highlighted in that article are all the result of ineffective systems.

Examples of unbalanced systems

  • The US financial system: While it seems highly efficient when working properly, a combination of forces have recently pulled it apart, leading to a global crisis.
  • Coordinating flights at airports: While most of the time, one can roughly count on reaching one's destination with only modest inconvenience, one snowstorm at one airport is enough to send dozens of airports all over the world into chaos. Running flights that are overbooked ensure no systematic way to pick up the slack when other flights are cancelled. Lack of preparation at airports for completely foreseeable weather events (e.g. snowstorms) cause cascading delays throughout the system.
  • Unforeseen supply chain interactions: (from [VS10])
    • “Peanut Corporation of America, a peanut-processing company based in Lynchburg, Virginia, whose sales were estimated at $25 million, triggered a $1 billion recall as its contaminated product found its way into some 2,000 products.”
    • “The toy company Mattel Inc., based in El Segundo, California, suffered substantial damage to its reputation in 2007 when a supplier to a supplier to a supplier to a supplier of Mattel chose to use lead-based ingredients that were outside Mattel’s specifications.”

Examples of balanced systems

  • The human body: Though not very efficient at all, the human body is effective in a broad range of activities.


Optimality is always relative. The optimum (best, most efficient) solution is always measured relatively too. Usually with respect to energy consumption or cost.

To be optimal in one context, means that the solution is (usually very) suboptimal in other contexts. So as conditions change, the highly optimal solution becomes brittle and loses optimality quickly.

Now consider looking at how efficiency changes for the same thing over multiple contexts. If one found a level of optimality that was the highest common possible value over the range of contexts, then one would have a suboptimal solution in any one context, but a maximally optimal solution in a broader range of contexts.

To do


  • Do we really mean efficacy or effectiveness?
    • From here, luminous efficacy is the light output of a light source divided by the total electrical power input to that source, expressed in lumens per watt (lm/W).
    • Rather like an efficiency, but where input & output are not measured in the same unit, but rather in units based on the purpose of a thing.
  • Can efficacy/effectiveness be defined in terms of a superposition of: robustness, resilience, adaptability,….
  • Need to operationalize/quantify the definition of effectiveness.
  • What if we defined efficiency as (useful output)/(all inputs + all useless outputs)?
  • Relate balance to the trade-off between effectiveness and efficiency.
  • Find other examples of unbalanced systems.
  • Find other examples of balanced systems.

See Also


AEO11. a M. Aurisicchio, N.L. Eng, J.C. Ortiz, P.N.R. Childs, and R.H. Bracewell. 2011. On the function of products. Intl Conf on Engineering Design. The Design Society. (link)
research/effectiveness_versus_efficiency.txt · Last modified: 2020.03.12 13:30 (external edit)