“You get 80% of the outcome you need from 20% of your effort, so just put in 20% that effort and you’ll get most of what you want.”
This idea stems from the Pareto Principle (also known as the 80/20 rule), which observes that roughly 80% of effects come from 20% of causes.
I’d heard the principle used this way in the past, but something about it never sat right. I want to briefly explore this to clarify my own thinking on the topic.
Jumping to the conclusion, the problem occurs when the rule is used as a justification for taking shortcuts or putting small amount of effort into a piece of work. The misapplication goes something like this:
- The Pareto Principle says 20% of work creates 80% of results
- Therefore, I only need to do 20% of the work
- I’ll just decide what that 20% is and ignore the rest
This fundamentally misunderstands what the Pareto Principle actually tells us. We can do better.
But before we get there, is there any truth here at all?
Is the Pareto Principle valid in the first place?
Probably not.
Before diving into how the principle should be applied, we need to address a more fundamental question: Is the 80/20 rule even valid to begin with?
The evidence suggests we should be sceptical. Despite its widespread acceptance, there is no scientific evidence that definitively backs up the Pareto Principle. It’s more a collection of anecdotal observations than a proven law of nature. Recent research directly contradicts the principle in marketing contexts, with studies showing that the 20% most valuable customers typically represent only about half of a brand’s business—not the claimed 80%. This ratio also varies significantly across industries.
The principle also suffers from several critical limitations:
- It focuses on a single factor while ignoring other variables that contribute to outcomes
- It assumes static relationships, yet consumers and markets constantly shift between categories
- It often leads to an overemphasis on a small number of factors at the expense of others
- The convenient “80/20” numbers rarely hold up to scrutiny, with actual distributions varying widely
- It can reinforce existing inequalities by directing even more resources to already dominant areas
So why discuss a principle that’s fundamentally flawed? Because despite its limitations, the Pareto Principle can still offer value—not as a planning framework, but as a retrospective learning tool. Even a flawed concept can be useful when applied correctly and with appropriate scepticism.
So what’s the problem?
The Pareto Principle originated when economist Vilfredo Pareto noticed that approximately 80% of Italy’s land was owned by 20% of the population. Similar distributions have supposedly been observed across numerous domains:
- 20% of bugs cause 80% of crashes
- 20% of features get 80% of user engagement
- 20% of clients generate 80% of revenue
Though these claims often lack rigorous verification, they’ve been repeated so often they’ve taken on the aura of truth. What’s important to understand is that even if these patterns do exist in some contexts, the principle is descriptive, not prescriptive. It describes patterns observed after the fact, not a formula to apply before starting work.
When we attempt to use Pareto as a planning tool, we immediately face a crucial problem: how do you know which 20% of activities will generate 80% of outcomes before you’ve done the work?
The reality is that you often can’t. The principle itself provides no mechanism for identifying which specific inputs will have disproportionate impact. It merely observes that some will.
This misinterpretation leads to half-baked work and frustration. In particular, it’s potentially toxic to hear from your leadership or manager:
- It communicates that low standards are OK here: “Just do 20% of the thing, right?”
- It leaves the (unknown) remainder of the work for others to pick up, which is abnegation of responsibility (“I already did the 80%! What was so hard for you?”)
- It can be used to dismiss high effort and intention (“Why are you overstretched? Just put in 20% of the effort!”)
Then there’s a deeper realisation: how do you know what is the right 20% in the first place? If we do only what we guess is the “critical 20%,” what we’ve actually done is 100% of the work necessary to achieve whatever outcome we got. The Pareto distribution still applies to that smaller scope of work.
Maybe more valuable application of the Pareto Principle comes when we shift from seeing it as a planning framework to recognising it as an iterative learning tool.
What could the principle be good for?
Instead of asking “What 20% of work should I do?” we should ask:
- What specific outcome do I want to achieve?
- What work seems necessary to achieve that outcome?
- After completing the work, which activities actually contributed most to success?
- How can I apply these insights to be more efficient next time?
This transforms the principle from a crude planning shortcut into a sophisticated tool for organisational learning and continuous improvement.
Consider a development team building a new feature. Instead of trying to guess which 20% of the feature set will deliver 80% of the value (and only building that), they:
- Define clear success metrics for the feature (focusing only on what they believe matters)
- Build a complete solution they believe will meet those metrics (doing their best to cut scope)
- After release, analyse which specific components drove the most user engagement or business value
- Apply those insights when prioritising future work
Over multiple cycles, the team develops pattern recognition skills that help them more accurately predict high-impact work. Each iteration refines their ability to focus effort where it matters most.
The true power of the Pareto Principle lies not in using it to do less work upfront, but in using it retrospectively to learn which types of efforts yield disproportionate results in your specific context.
This learning doesn’t happen in a single cycle. It requires iteration, measurement, and reflection. Over time, teams develop an increasingly refined sense of where their efforts generate the greatest impact.
So the next time someone suggests “Let’s just focus on the 20% that matters,” the appropriate response might be: “We don’t know yet which 20% that is. Let’s complete this work, measure what drives results, and apply those insights to our next project.”
That’s how we transform the Pareto Principle from a misunderstood excuse for corner-cutting into a power tool for continuous improvement and organisational learning.