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The 80-20 Rule of Analysis and Optimization

Level 9

The Pareto Principle

The Pareto principle, also known as the 80-20 principle, says that 20% of the issues will cause you 80% of the headaches. This principle is also known as The Law of the Vital Few. In this post, I'll describe how the Pareto principle can guide your work to provide maximum benefit. I'll also describe a way to question the information at hand using a technique known as 5 Whys.

The 80-20 rule states that when you address the top 20% of your issues, you'll remove 80% of the pain. That is a bold statement. You need to judge its accuracy yourself, but I've found it to be uncannily accurate.

The implications of this principle can take a while to sink it. On the positive side, it means you can make a significant impact if you address the right problems. On the down side, if you randomly choose what issues to work on, it's quite likely you're working on a low-value problem.

Not quite enough time

When I first heard of the 80-20 rule I was bothered by another concern: What about the remaining problems? You should hold high standards and strive for a high-quality network, but maintaining the illusion of a perfect network is damaging. If you feel that you can address 100% of the issues, there's no real incentive to prioritize. I heard a great quote a few months back:

     "To achieve great things, two things are needed; a plan, and not quite enough time." - Leonard Bernstein

We all have too much to do, so why not focus our efforts on the issues that will produce the most value? This is where having Top-N reports from your management system is really helpful. Sometime you need to see the full list of issues, but only occasionally. More often, this restricted view of the top issues is a great way to get started on your Pareto analysis.

3G WAN and the 80-20 rule

A few years back, I was asked to design a solution for rapid deployment warehouses in remote locations. After an analysis of the options I ran a trial using a 3G-based WAN. We ran some controlled tests, cutting over traffic for 15 minutes, using some restrictive QoS policies. The first tests failed with a saturated downlink.

When I analyzed the top-talkers report for the site I saw something odd. It seemed that 80% of the traffic to the site was print traffic. It didn't make any sense to me, but the systems team verified that the shipping label printers use an 'inefficient' print driver.

At this point I could have ordered WAN optimizers to compress the files, but we did a 5 Whys analysis instead. Briefly, '5 Whys' is a problem solving technique that helps you identify the true root cause of issues.

  • Why is the bandwidth so high? - Printer traffic taking 80% of bandwidth
  • Why is printer traffic such a high percentage? - High volume of large transactions
  • Why is the file size so large? - Don't know - oh yeah we use PostScript (or something)
  • Why can't we use an alternative print format? - We can, let's do it, yay, it worked!
  • Why do we need to ask 5 whys? - We don't, you can stop when you solve the problem

The best form of WAN optimization is to suppress or redirect the demand. We don't all have the luxury of a software engineer to modify their code and reduce bandwidth, but in this case it was the most elegant solution. We were able to combine a trial, reporting, top-N and deep analysis with a flexible team. The result was a valuable trial and a great result.


Here's a quick summary of what I covered in this post:

  • The 80/20 principle can help you get real value from your efforts.
  • Top-N reports are a great starting point to help you find that top 20%.
  • The 5 Whys principle can help you dig deeper into your data and choose the most effective actions.

Of course a single example doesn't prove the rule.  Does this principle ring true for you, or perhaps you think it is nonsense? Let me know in the comments.


Ah yes, the 80-20 rule.  It applies to so many things in IT.

This did provide an excellent example though.

Level 11

It is a great principle!


I like to apply the 80-20 rule to event management as well.

with a little of work you can easily handle 80% of your event traffic with a few alert rules if built properly.

This allows you to concentrate more time on the 20% that likely require one-off alerts and other customized monitoring.

Human nature seems to be responsible for the Five Why's.  Folks could avoid them by admitting "This broke or failed because we (pick your answer or build a more appropriate one for your situation)

  • were too lazy to do it right
  • were ignorant of the facts
  • had to bow to a VIP that was a squeaky wheel
  • chose to compromise policy rather than offend a VIP
  • reprioritized funding for someone else's projects

I like the idea of 80-20 being recognized and used to predict and reduce incidents.

Level 14

Good example.  I have used this rule in the past concerning people.  20 percent of the people get 80 percent of the work done.

Level 20

Makes me think about Security Event ID 4656 and handle manipulation.  When security policy is enabled it can blow up your security event log collector.  So in this case such a small change in secpol ends up almost bringing the collection of Windows Security Event Logs to it's knees.  I'm still working on way to capture the handle manipulation I want to see without millions of events about the OS and SEP both just doing normal business of running throughout the day... in this case it's more like 5%/95% o.O!

Oh man... my skin is crawling while I read this. 80/20... <shiver>

I interpret the 80/20 rule as an opportunity to cut corners and brush things under the run. And far too often those things have come back and bit me in the butt later down the road. I'm a process junkie and my motto as a service delivery manager has been, "I don't want it fast! I want it right!" However, I love that Leonard Bernstein quote. I might have to consider changing the one in my digital signature:

    "Give me six hours to chop down a tree and I will spend the first four sharpening the axe." - Abraham Lincoln

In fairness, I can say that my mindset has won me very little favors with my leadership. However, I am a man of conviction.


Ah...chainsaw appreciation day !

Level 13

So agree with network defender​ on the 20 percent of people cause 80 percent of my problems. 

Level 14

So true... the forgotten few who make it all happen.

Level 9

I use the 80/20 rule when writing my performance self evals as well... outstanding 80% of the categories good the other 20% makes it look like you've deeply considered your strengths and weaknesses.

We also use the 5 whys when doing post incident reviews after each critical incident. The teams hate them but at least we are beginning to cut down on the number of repeat mistakes causing the same issue.

Level 11

I've been troubleshooting for quite a long time and this is the first time I'd heard of the five whys notion. Thanks for linking the wiki page, it was quite a good read as well!

Also -- really liked your fifth "why".

Level 17

I'll consider the answers to all our IT issues a Fifth at a time


cahunt​, a musical fifth?, like a fifth of Beethoven or a fifth (actually a 750ml these days)  of fine spirits ?

Level 14

Single Malt?


that works too.

Level 17

Always!     If it's not a scotch moment the Cognac comes out 2 oz at a time.

Level 17

D. All of the Above Good Sir!

* Was actually working out some fifth's and Seventh's accent a G/C progression last night for a song/project I am currently working on. 
  * I think Chopsticks was played somewhere in there, along with Linus and Lucy... before some War Pigs..(not quite Beethoven, but the original content we do could certainly rival Beethoven during his Punk Phase he went through)
  * Potato-E V stored just in case you have issues with Corn and Deep Eddy's Customs for a great Arnold Palmer. No Plastic Bottles, Fine is an understatement, but don't go at it alone or you might just end up singing a Willie song when you wake up at 10.


cahunt​ ROFLMAO !

Level 12

Really like this topic.  I think it will be interesting to try applying the five why analysis to issues as they arise.  It's difficult enough to get prioritization (everything's always a priority), but asking why should be interesting.

Level 9

Thanks for the comment. It's nice to see you're getting results with the five why's process. It can be frustrating, but when the engineers reflect honestly, we'd much the slight pain of highlighting persistent issues so that we can stop making the same mistakes again and again.

Level 9

Glad you liked the post.  It's a really useful technique to drive root cause analysis.  Some folks won't like your addintional questions but if you explain that you're looking to do the 'right thing for the business' that will help.

Level 21

This is such a great and well timed post.  My manager was just recently telling me how we need better implementation of the 5-why system.  Often our clients come to us with solutions instead of problems.  We often can see that these solutions are not good but the problem has always been breaking it down to really understand the problem they are trying to solve so we can propose a better solution.  We have found the best way to do this is using the 5-why's. 

About the Author
"John Harrington is a network engineer who loves network design, deployment and testing. He has designed and deployed enterprise, mobile telecoms and public cloud data center networks. He values efficient processes and business-driven networking. John enjoys sharing his mistakes, learnings, and insights on his blog The Network Sherpa and on Twitter."