This is post 9 of 9 in our Little's Law series.
I personally can't fathom how someone could call themselves a flow practitioner without a concerted effort to study Little's Law. However, the truth is that some of the posts in this series have gone into way more detail about LL than most people would ever need to practically know. Having said that, without an understanding of what makes Little's Law work, teams are making decisions every day that are in direct contravention of established mathematical facts (and paying the consequences).
To that end, for those who want to learn more, here is my suggested reading list for anyone interested in learning more about Little's Law (in this particular order):
1. http://web.eng.ucsd.edu/~massimo/ECE158A/Handouts_files/Little.pdf Frank Vega and I call this "Little's Law Chapter 5" as it is a chapter taken from a textbook that Little contributed to. For me, this is hands down the best introduction to the law in its various forms. I am not lying when I say that I've read this paper 50 times (and probably closer to 100 times) and get something new from it with each sitting.
2. https://people.cs.umass.edu/~emery/classes/cmpsci691st/readings/OS/Littles-Law-50-Years-Later.pdf This is a paper Little wrote on the 50th anniversary of the law. It builds on the concepts of Chapter 5 and goes into more detail about the history of L=λW since its first publication in 1961. This paper, along with Chapter 5, should tell you 95% of what you need to know about LL.
3. http://fisherp.scripts.mit.edu/wordpress/wp-content/uploads/2015/11/ContentServer.pdf Speaking of the first publication of the proof of L=λW, there's no better teacher than going right to the source. This article would be my 3rd recommendation as it is a bit mathy, but its publication is one of the seminal moments in the history of queuing theory and any buff should be familiar with this proof.
For extra credit:
4. http://www.columbia.edu/~ww2040/ReviewLlamW91.pdf This article is not for the faint of heart. I recommend it not only for its comprehensive review of L=λW but also (and mostly) for its exhaustive reference list. Work your way through all of the articles listed at the end of this paper, and you can truly call yourself an expert on Little's Law.
If you read all of these, then you can pretty much ignore any other blog or LinkedIn post (or Wikipedia article, for that matter) that references Little's Law. Regardless of the effort that you put in, however, expertise in LL is not the end goal. No, the end goal is altogether different.
Why You Really Should Care
If you are studying Little's Law, it is probably because you care about process improvement. Chances are the area of process improvement that you care most about is predictability. Remember that being predictable is not completely about making forecasts. The bigger part of predictability is operating a system that behaves in a way that we expect it to. By designing and operating a system that follows the assumptions set forth by Little's Law, we will get just that: a process that behaves the way we expect it to. That means we will have controlled the things that we can control and that the interventions that we take to make things better will result in outcomes more closely aligned with our expectations. That is to say, if you know how Little's Law works, then you know how flow works. And if you know how flow works, then you know how value delivery works.
I hope you have enjoyed this series and would welcome any comments or feedback you may have. Thanks for going on this learning journey with me!
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About Daniel Vacanti, Guest Writer
Daniel Vacanti is the author of the highly-praised books "When will it be done?" and "Actionable Agile Metrics for Predictability" and the original mind behind the ActionableAgile™️ Analytics Tool. Recently, he co-founded ProKanban.org, an inclusive community where everyone can learn about Professional Kanban, and he co-authored their Kanban Guide.
When he is not playing tennis in the Florida sunshine or whisky tasting in Scotland, Daniel can be found speaking on the international conference circuit, teaching classes, and creating amazing content for people like us.