The Pareto Principle

Mental models help us simplify complexity, direct our attention, and make better decisions when time and information are limited. One of the most useful—and widely applicable—is the Pareto Principle. Often called the “80/20 rule,” the Pareto Principle describes a pattern that appears across many domains: A relatively small share of causes tends to drive a large share of results. The exact ratio varies, but the underlying idea is consistent: importance is often concentrated, not evenly distributed. This makes the Pareto Principle a powerful mental model—before treating everything as equally important, ask whether a small number of items are doing most of the work. When that pattern is present, attention and effort should be concentrated where impact is greatest.Financial reporting provides an example of how this mental model can be applied. In many areas of financial reporting, a small number of items account for most of the total value, while a large number of smaller items have little influence on a user’s understanding of financial condition. A common example is capitalized assets. A handful of assets make up a very large portion of the total value. GFOA examined the assets of more than 60 governments and found that 20 percent of the most expensive assets made up more than 80 percent of the total reported value. Seen through the Pareto lens, this suggests a different approach. Instead of distributing effort evenly, we can align it with where it matters most. This is the idea behind GFOA’s work on rethinking materiality. Materiality is not about eliminating all error. It is about preventing decision-relevant error—the kind that could mislead users about financial condition or performance. Applying the Pareto Principle raises some questions.