Some ideas based on numbers or ratios are valuable and worth remembering.
One of these is "Seven Plus or Minus Two."
The idea of “7 plus or minus 2” comes from psychologist George A. Miller, who showed that human mental capacity is limited. In simple terms, people can only handle a small number of items, decisions, or relationships at once.
The concept was introduced by George A. Miller in his famous 1956 paper, “The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information”.
Miller studied how people process information such as numbers, sounds, and patterns. He found that people tend to handle around 5 to 9 pieces of information at one time in their short-term memory.
The key insight was not the exact number, but the principle: human cognitive capacity is limited. When too much information is presented, performance declines.
In business, this has a powerful implication: there is a limit to how many people, tasks, or decisions one manager can effectively handle. As a rule of thumb, a manager can supervise up to 9 people when work is simple and repetitive, but only around 5 people when work is complex and requires judgment.
This principle helps design better organisations, improve decision-making, and avoid overloading managers.
When managers are overloaded, common problems appear:
❌ slow decisions
❌ poor follow-up
❌ weak coaching
❌ inconsistent standards
❌ constant firefighting
🟢 7–9 reports → simple, repetitive work
🟡 5–7 reports → mixed complexity
🔴 3–5 reports → complex, technical work
Complexity reduces capacity. Simplicity increases it.
❓ How many direct reports does each manager have?
❓ Is the work simple and repetitive, or complex and variable?
❓ How many decisions and exceptions does each manager handle weekly?
❓ Are managers coaching staff or constantly firefighting?
❓ Could better systems increase capacity?
❓ Are some teams too large for the complexity involved?
❓ Do your structures reflect real managerial capacity?
Author: George A. Miller
Key Work: The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information (1956, Psychological Review)
Related Book: Psychology: The Science of Mental Life (George A. Miller)