Vilfredo Pareto, a turn-of-the-century Italian economist,
studied the distributions of wealth in different countries,
concluding that a fairly consistent minority – about 20%
– of people controlled the large majority – about 80%
– of a society's wealth. This same distribution has been
observed in other areas and has been termed the Pareto
The Pareto effect even operates in quality improvement: 80% of
problems usually stem from 20% of the causes. Pareto charts are
used to display the Pareto principle in action, arranging data so
that the few vital factors that are causing most of the problems
reveal themselves. Concentrating improvement efforts on these few
will have a greater impact and be more cost-effective than
Things to look for:
In most cases, two or three categories will tower above the
others. These few categories which account for the bulk of the
problem will be the high-impact points on which to focus. If in
doubt, follow these guidelines:
- Look for a break point in the cumulative percentage line.
This point occurs where the slope of the line begins to flatten
out. The factors under the steepest part of the curve are the
- If there is not a fairly clear change in the slope of the
line, look for the factors that make up at least 60% of the
problem. You can always improve these few, redo the Pareto
analysis, and discover the factors that have risen to the top now
that the biggest ones have been improved.
- If the bars are all similar sizes or more than half of the
categories are needed to make up the needed 60%, try a different
breakdown of categories that might be more appropriate.
Often, one Pareto chart will lead to another:
- before and after charts
- charts that break down the most important factors discovered
in an earlier chart
- charts that use different scales, such as number of
complaints and the cost to respond, with the same
Pareto chart statistics:
For the Pareto chart, the following overall statistics are
||the average of all the values in the
series, i.e. the average bar height.
||the sum of all the values in the
If you are using the AutoPareto mode, the following
statistics are also calculated for each class of data:
||The number of items in that class
||The percentage of the whole data set
which that bar accounts for.
Create Pareto Charts using PathMaker's Data Analyst tool.