What does "variety" measure?

The concept of "variety" will come up regularly in these article posts, so I shall give a short overview of what is meant by it.

This term, "variety", is not being used strictly in its usual colloquial sense, rather it has a technical meaning (that also has reference to its colloquial meaning).

It is a term that was introduced by W. Ross Ashby, a pioneer in the field of cybernetics, which is the study of the science of communications and control systems pertaining to machines and living things.

The story of its introduction is that the "father" of information theory, Claude Shannon had introduced a measure of information that he termed "entropy", in 1949, expressed in a law now known as "Shannon's law".

Where "entropy" was a statistical measure of uncertainty, "variety" was somewhat related, measuring the number of possible states of a system.

Ashby said that the concept of variety was inseparable from that of information.

This concept of "variety" enabled Ashby to build his theory of homeostasis (synonymous with regulation, governance, or control etc.). It in effect expressed Shannon's law more generally, potentially covering a much wider field than just information and communication theory.

This scientific background aside, the concept was found to be highly applicable to modern management thought, primarily through the work of Professor Stafford Beer.

He asserted that managing complexity was the essential task of management, and that this concept or measure of "variety" was central to it.

"It has always seemed to me that Ashby’s Law stands to management science as Newton’s Laws stand to physics". (Professor Anthony Stafford Beer)

Beer demonstrated for instance that "variety" needed to be managed actively along all communication channels between "environment and operations", and "operation and management".

The challenge that managers are faced with, in a nutshell, is that every move made that constrains or controls complexity or "variety" also blocks off opportunity.

For a deeper "dive", with examples that should make things clearer, this concept will typically be an early topic introduced in any training or coaching engagement (expressed in simple easily understandable managerial english rather than in mathematical equations).

In the meantime, you may think of the term as almost synonymous with complexity. I.e. "Variety" is a measure of complexity.