Does the Pareto Principle Always Hold? A Note and the "Working Ant" Story

"80% of sales come from 20% of products." "Most of an organization's results are produced by a handful of people." The Pareto principle, and the "working ant story" attached to it, are often cited as the basis for such claims. Only some ants work hard; the rest barely work. And even if you gather only the hard workers, slackers appear again among them. At first glance it seems to apply directly to human organizations—but does the Pareto principle really always hold? This article reviews the meaning of the Pareto principle, then unpacks what the working-ant law actually says, why the two are frequently conflated, and the important caveat that it "does not necessarily hold."

What Is the Pareto Principle?

The Pareto principle is an empirical rule that "most of a whole's results are produced by a small portion of its elements." It originates from the Italian economist Vilfredo Pareto, who, while studying income distribution, discovered the skew that "about 80% of a society's wealth is held by about 20% of people." From that ratio it is also called the "80-20 rule" or the "2:8 rule."

In business, it is often expressed in forms like the following.

• 80% of sales are produced by 20% of all customers (top customers)
• 80% of sales are accounted for by 20% of all products (best sellers)
• 80% of results come from 20% of the time you spent

What's important is that the "80-20" figure itself is only a guide. In reality it can be 70-30 or 90-10, and the essence of the Pareto principle is the tendency that "results concentrate, skewed toward a portion of the elements." For the meaning and business use of the principle, see our separate article "What Is the Pareto Principle? The Meaning of 80-20, Business Uses, and Examples".

What Is the "Working Ant Law"?

Often told together with the Pareto principle is the "working ant law." This is a story grounded in biological observation: when you observe a colony of ants, the following tendencies are said to appear.

• Hard-working ants are only a portion: Within a colony, the ants that work diligently are about 20%, ordinary workers 60%, and ants that barely work 20%—the so-called 2:6:2 split.
• Gathering only the workers gives the same result: Even if you extract only the hard-working 20% and form a new colony, ants that don't work appear again among them, and the makeup returns to roughly 2:6:2.
• The idlers have a role too: Rather than everyone working at full power all the time, some ants resting helps avoid a simultaneous collapse from exhaustion, allowing the colony to be sustained longer—so research suggests.

Because the structure of "the top 20% carry most of the output" resembles the Pareto principle, the working-ant story has been widely cited as a familiar example of the Pareto principle and as a metaphor in organizational theory.

The Relationship Between the Pareto Principle and the Working Ant Law

The two resemble each other in that "20% supports the whole," but strictly speaking they are different things. To avoid confusion, let's organize the distinction.

• Pareto principle: An empirical rule expressing "the skew of results" in economics, sales, output, and the like. Its subject is numbers such as wealth or sales.
• Working ant law: A biological observation about the "distribution of labor" in an ant colony, and the fact that the same makeup is reproduced even when the colony is divided.

In other words, while the Pareto principle is about the skew that "results concentrate in a very small portion," the working-ant law carries a slightly different implication: "the structure where some rest has meaning, and moreover that structure is reproduced." The two are often linked to claim "therefore 20% of an organization supports the whole," but this is best understood as nothing more than a metaphor.

The Pareto Principle Does Not Necessarily Hold

This is the heart of the article. The Pareto principle is a handy rule of thumb, but it is not a law that "holds at 80-20 for any subject at any time." Here are the points to watch.

1. 80-20 Is Only a Rough Guide

As noted above, the ratio changes by subject. When you actually aggregate data, the skew can be mild like 60-40, or extreme like 90-10. If you assume "it must come out to 80-20" and force the data to fit, you'll misread reality. What matters is not the ratio figure but confirming with real data "whether there is a skew, and if so, to what degree."

2. Some Fields Have Small Skew or Are Dispersed

Not every phenomenon concentrates in a portion. For goods like everyday consumables that many customers buy roughly equally, the concentration in the top 20% is low. In recent years, with the spread of the internet, the "long tail" phenomenon—where the accumulation of niche products generates large sales—has also drawn attention. Contrary to the Pareto principle, this is a case where "the many at the bottom" hold value that can't be ignored, showing that not everything can be explained by top-end concentration.

3. "Working Ant" Does Not Mean "It's OK to Slack"

Applying the working-ant law to human organizations and interpreting it as "20% won't work anyway, so it can't be helped" or "I can be the 20% that doesn't work" is a mistake. What the ant research shows is the ecology that "a structure where some rest helps the colony survive," not that a specific individual may slack off. In human organizations, many factors are intertwined—evaluation systems, role allocation, motivation—and you cannot apply the ant observations directly.

4. It's Only Correlation/Tendency, Not Causation

The Pareto principle is not a theory explaining "why it happens," but an empirical rule that "such a skew tends to be observed as a result." Just because something fits the rule, jumping to "strengthen that 20% and results will surely grow" is dangerous. The bottom 80% may contain seeds that will grow from here.

Points for Using It in Business

Taking into account that it "does not necessarily hold," it's realistic to use the Pareto principle as follows.

1. First, confirm the skew with your own real data: Don't assume 80-20; actually aggregate sales and customers and grasp how concentrated things are.
2. If concentrated, allocate resources to the priority: If results are skewed toward the top, you can raise efficiency by weighting measures toward that segment.
3. Don't discard the bottom (tail): Customers or products that are small individually but many in number can hold large value across the whole. Avoid easy cutoffs.
4. Review periodically: The structure of the skew changes over time. Don't fix it with a single analysis; verify it continuously.

A representative method for grasping this "skew" is ABC analysis, which classifies items into A, B, and C by contribution. For how to do it in practice, see our separate article "What Is ABC Analysis? Meaning, Calculation, and How to Measure Effectiveness".

Summary

The Pareto principle is a useful rule of thumb that "results tend to concentrate, skewed toward a portion of the elements," and the working-ant law is often cited as a familiar metaphor for it. However, the 80-20 ratio is only a guide; depending on the subject the skew may be mild, or the many at the bottom may hold value as in the long tail—so it does not necessarily hold as stated. Interpreting the working-ant story as "grounds for slacking off" is also a mistake. What matters is not to take the rule at face value, but to confirm with your own real data whether and to what degree a skew exists, and to keep an eye on both priority allocation to the top and the value of the bottom. Use the rule of thumb as a starting point for thinking, and entrust the final judgment to the actual numbers—that is the right way to engage with the Pareto principle.