The Pareto Principle in Software Engineering

In software engineering, efficiency is often the key to success. The Pareto Principle, also known as the 80/20 rule, offers a framework to focus effort where it matters most. This principle suggests that 80% of results come from 20% of the effort - an insight that can really shape how software teams can organise their tasks, manage collective efforts, and consequently deliver the value that matters most.

In today’s Theory Thursday article, we’ll explore how the Pareto Principle applies to our world of software engineering, how it can impact productivity (for better or worse), as well as how to use it to its best potential.

What is the Pareto Principle?

The Pareto Principle was named after Italian economist Vilfredo Pareto, who in the late 19th century, noted that 80% of Italy’s wealth was owned by only 20% of its entire population. This concept has since been extrapolated to suggest that a small percentage of causes often leads to a majority of effects in various contexts, of which software development is one of them!

In software engineering, the Pareto Principle can take a number of forms:

• 80% of software usage comes from 20% of features
• 80% of bugs arise from 20% of the codebase
• 80% of development time is often spent on 20% of tasks

The key is to identify what the critical 20% is and maximising it to our potential.

Applying the Pareto Principle

Let’s take a look through a number of different lenses to see how the Pareto Principle could be used within a software engineering context.

Prioritise Features

It probably comes as no surprise that most features in an application are not providing a great deal of value. For example, animations on a UI look great and add a sense of finesse, but they’re definitely not a critical part of the application’s functionality. Similarly, have social integrations to share content which typically wouldn’t be shared by people (e.g. on your personal health record from your GP/practitioner’s system) makes little to no sense.

Using the Pareto Principle / mindset, we can use data to inform how we go about building and prioritising features. Use things like analytics, user feedback, A/B testing to identify where the most value values, and prioritise using this.

It’s better to have a bug-free, fully-functioning service than something which breaks regularly yet allows you to switch between light and dark mode (although dark mode is definitely a winner).

Focus on the 20% of features which deliver 80% of the value.

Optimise Bug Fixing

It is a known fact that the majority of bugs will originate from a smaller section of an application’s codebase, usually legacy.

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