80/20 Rule in Software Development

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80/20 Rule in Software Development

With agile business practices gaining prominence and wider adoption, organizations want results that are not only efficient but also quick. To ensure that agility doesn’t come at the cost of quality, thorough analysis, strategic planning, and a lot of smart work is required.

The adoption of 80/20 principle in software development can help you do just that. You can save time, effort and money while unfailingly achieving your development goals.

What is the 80/20 Rule?

The 80/20 rule or principle is also known as the Pareto Principle, originally proposed by Italian economist, Vilfredo Pareto. The principle establishes a correlation between cause and effect, stating that 80% of life’s consequences or effects are caused by 20% of causal events. While studying the social and economic indicators of Italian population in the 1800s, Vilfredo Pareto postulated that 80% of the nation’s income and real-estate ownership is controlled by only 20% of the population.

This led to the proposal of the 80/20 rule, which eventually got popularized as a fundamental cause-effect principle. Over the years, the rule found application in quality control, sales, and marketing. Some of its popular applications are-

  • 80% of manufacturing defects are caused by 20% of manufacturing mistakes.
  • 80% of profit comes from 20% of customers.
  • 80% of sales revenue is generated by 20% of sales executives.
  • 80% of employee productivity comes from 20% of the time invested.

How the 80/20 Rule is Relevant in Software Development?

This simplistic but functional approach also found application in software development, starting with the attribution of 80% of errors to 20% of code. From a tech perspective, it applies to:

  • 20% of website content leading to 80% of website traffic.
  • 20% of app/ software features being used 80% of the time by majority users.
  • 20% of code bugs cause 80% of code performance issues.
  • 20% of tech skills being useful for 80% of the software development roles.

Even though the rule is very numeric on the face of it, the idea is not to fixate on numbers and accept that input is not always directly proportional to output. For some software applications, for instance, exactly 20% of the features won’t be the most used ones. It may be 17% or 23% or any number representing the most popular features.

Similarly, it’s not necessary that all users will use these top features exactly 80% of the time. Some users may have very niche requirements and prefer more obscure features over the popular ones. Also, maybe only 80% of the users will use these features but not 60% of the time.

Application of the 80/20 Rule

More than anything else, what the 80/20 rule has done is made it possible for software developers and managers to approach development in a more agile and efficient manner. By narrowing the scope of causal elements in software adoption, performance, and failure; developers have been able to prioritize their actions for smoother user experience. And some prime areas for the application of 80/20 rule in software development are:

Development of Minimum Viable Products (MVP): When developing a new software application or product from scratch, all possible features and functionalities have to be thoroughly considered. More the features, lengthier and more complex the code. However, ironically, even users who seek feature rich applications end up using only about 20-30% of these features regularly.

It makes perfect sense to, thus, launch an MVP version of software with these 20% features that attract most user interest. Appropriate feature selection during software development not only saves time in product building, it also improves product relevance for early adopters and increases application usage post introduction.

Software Testing and Bug Elimination: It’s common to find a problematic piece of code during software testing that can make the whole application crash. This code may be as little as 20% of the code but whenever it’s fixed, new bugs can appear around it as a side effect.

Following the 80/20 rule, testers can always start the bug elimination process by prioritizing a check of such bug clusters. 80% of the time, the error can be found and fixed there.

Code Optimization: Just like there exists bug clusters in about 20% of the code, there are hot-spots of code that require regular review and optimization. It’s the very same code that controls the most used features and, therefore, has to be effectively refactored. Unfortunately, repeated code improvements can lead to code lengthening and the code losing its structure.

By identifying the code that needs to be repeatedly optimized, overhauled, or completely rewritten, and refactoring it properly, code maintenance can be simplified. Code access and change logs can be analyzed over a period of time to determine 10-20% of code segments that are most tweaked. All refactoring efforts can be prioritized from there on.

Project Strategy and Management: The Pareto Principle also finds application in long term strategizing and management of software development projects. Since certain software functionalities have to be prioritized over others, to achieve agility, 80% of the team can be deployed for building those 20% of core functions.

The remaining 20% of manpower can be engaged in developing 80% of the features which are of lesser relevance. Not only does this reduce the overall risk of project failure, it makes project management smoother with higher visibility of team engagement.


In conclusion, the 80/20 rule helps tech managers in determining how a small percentage of causal elements can affect the outcomes or net performance of a software product or service. Applied flexibly, it can save software development companies time, money, and resources while resulting in software products that can meaningfully elevate user experience.