Pareto Analysis (The 80/20 Rule)
Pareto Analysis ranks your causes or problems by impact and shows that a small fraction of them account for most of the effect, so you fix the vital few instead of spreading effort across the trivial many.
Five steps run left to right, from logging every cause through to fixing only the vital few that account for most of the damage.
Reach for this when…
- Complaints, defects or costs are piling up and you don't know where to start.
- Everyone has a pet cause for a problem and you need data to settle the argument.
- You have limited time this quarter and need to know which fix will move the needle most.
How to run it
- List every distinct cause or category contributing to the problem.
- Measure or count the impact of each: cost, frequency, time, whatever the problem is measured in.
- Rank causes from largest impact to smallest.
- Calculate the running cumulative percentage as you go down the list.
- Draw the line where roughly 80% of the effect is accounted for. Fix those causes first.
A worked example
Situation. Sarah Mitchell ran Mitchell Textiles, a dyeing and weaving operation in Adelaide, Australia, fielding constant complaints about late deliveries and blaming everything from customs to weather.
Applied. She logged every delay for six weeks and ranked the causes by days lost. Two causes, a single overloaded dye vat and one unreliable transporter, accounted for most of the total delay.
Result. She added a second vat and switched transporters. Late deliveries dropped sharply within the next cycle, without touching customs or the weather at all.
The catch
The 80/20 split is a rule of thumb, not a law - some datasets are flatter, some are more extreme, and forcing the ratio onto the data distorts the picture. It also identifies where the impact sits, not why, so treat it as the start of the investigation, not the end.
Fixing the biggest bar on the chart only helps if that cause is still active. Check the data is current before you act on it.
Origin: Vilfredo Pareto; popularised by Joseph Juran