Goodhart’s law is a much quoted adage that states: When a measure becomes a target, it ceases to be a good measure’.
When we see numbers cited as evidence, we tend to instinctively give them more credibility than they may deserve. Without an examination of the source and scope of the numbers, just believing them on face value can lead to very bad choices.
Charles Goodhart is a prominent British monetary economist. His public profile started as a footnote to a 1975 article and read: ‘any observed statistical regularity will tend to collapse once pressure is placed upon it for control purposes’. It took on its now well-known form, above, when restated by an anthropologist seeking to link the idea to a much wider context than economics.
In almost every business I visit, I see examples of Goodhart’s law. The most common is the use of EBIT as a measure of success. The reality however, is that it is simply a financial measure of the outcome on the myriads of smaller actions and decisions that have been taken in the deployment of resources.
Two of the most public failures of measurement should make us all wary of using quantitative targets as a measure of performance.
The 2010 Volkswagen software scam. VW installed software in a range of cars with their turbocharged direct injection diesel engines that ensured that when being tested, the cars made the emissions standard of the US EPA.
The Vietnam War body count. The US defence department sought to justify the billions of dollars and thousands of lives expended in the defence of a corrupt government in South Vietnam. The measure became the body count of VC fighters and North Vietnamese regulars, which led to wholesale slaughter. These imaginary and bloody numbers were used for years as the basis for increasing commitment. It finally became obvious that they did not in any way reflect the ability or willingness of much of the population to fight what they saw as aggression by the US.
There are thousands of examples. If you looked, you would see them every day, especially when politicians open their mouths and quote numbers.
Header Photo: Charles Goodhart. Professor Emeritus at the London School of economics.
PS. When you look at the header, Dr. Goodhart is looking directly into your eyes. You will tend to believe anything he tells you.
