Close this search box.
Close this search box.
Close this search box.

Peer Code Review – Benefits and Statistics


Benefits and statistics of embedding peer code review into your software development process.

As a Lean-Agile coach, I regularly talk with software development groups about the benefits of adding code review to their development process. Some easily embrace it and some require a little bit of persuasion, but usually, I find enough internal allies to initiate the change. Lately, I encountered a whole group that completely rejected this essential practice as a luxury they can not afford. Explaining that they will see immediate ROI within a sprint or two was not enough to convince them. So, I sat to compose the following list and sent it to the group. Luckily I had a sympathetic ear with the general manager of the business unit who embraced it and made it easier for the team to experiment with the practice. All’s well that ends well… here is the list, shared with you too.

Code review is a software quality assurance practice in which one or more developers, called “reviewers”, inspect program code by viewing, reading, and checking it. At least one reviewer is not the code author. Peer code review is done by peer programmers, usually one.

So why should you deploy code review? Here are some of the benefits:

  1. BIQ – Builds quality into your process with the best ROI
  2. Fewer defects in your code – by more than 80%, see the next section below for more details
  3. The cost of software defects is lower the earlier they are detected, x10, x100, and even x1000 times – it starts with collaborative story writing and continues with peer code review
  4. Builds peer pressure on code quality due to the Ego Effect – People will write better code when they know their code is going to be “reviewed”
  5. Knowledge sharing between team members promotes internal learning
  6. Provides opportunities for mentoring junior developers – junior developer can review the mentor’s code and the mentor can review the junior’s code, both practices will support the junior’s development
  7. Supports the development of T-shaped professionals – T-shaped people are experts in one area but understand enough in other domains to support the continuous flow of the development process
  8. Removes the notorious single-point of failure manifested by the one expert developer
  9. By discussing and collaborating on code its readability is inherently improved
  10. Code standardization – style of code becomes similar in the team and thus more readability, better support, and maintenance
  11. Technical collaboration results in better estimates and better planning of efforts ahead
  12. Provides another checkpoint that requirements are fulfilled

Apparently, as seen in the following list of statistics, code review is the most effective practice you can embed into your software development process to strengthen BIQ (built-in quality).

Steve McConnel in his book CodeComplete provides the following statistics:

“… software testing alone has limited effectiveness – the average defect detection rate is only 25 percent for unit testing, 35 percent for function testing, and 45 percent for integration testing. In contrast, the average effectiveness of design and code inspections is 55 and 60 percent. Case studies of review results have been impressive:

  • In a software-maintenance organization, 55 percent of one-line maintenance changes were in error before code reviews were introduced. After reviews were introduced, only 2 percent of the changes were in error. When all changes were considered, 95 percent were correct the first time after reviews were introduced. Before reviews were introduced, under 20 percent were correct the first time.
  • In a group of 11 programs developed by the same group of people, the first 5 were developed without reviews. The remaining 6 were developed with reviews. After all the programs were released to production, the first 5 had an average of 4.5 errors per 100 lines of code. The 6 that had been inspected had an average of only 0.82 errors per 100. Reviews cut the errors by over 80 percent.
  • The Aetna Insurance Company found 82 percent of the errors in a program by using inspections and was able to decrease its development resources by 20 percent.
  • IBM’s 500,000-line Orbit project used 11 levels of inspections. It was delivered early and had only about 1 percent of the errors that would normally be expected.
  • A study of an organization at AT&T with more than 200 people reported a 14 percent increase in productivity and a 90 percent decrease in defects after the organization introduced reviews.
  • Jet Propulsion Laboratories estimates that it saves about $25,000 per inspection by finding and fixing defects at an early stage.”

A couple of notes:

Are there any downsides to code review?

Apparently, it takes time, but most often it saves more time already within the same Sprint !!!

Code review may be done with a peer, tech expert, manager, or group of peers. It has siblings such as pair programming, and group programming. Each practice has its own benefits and all are worth practicing.

However, research suggests that the most cost-effective practice with the highest return on investment is “peer code review” where peers in the team review each other’s code.

So what are you waiting for? Go and try it.

Subscribe for Email Updates:



Business Agility
Continuous Deployment
Release Train Engineer
Product Ownership
Lean Agile
Agile and DevOps Journey
Story Slicing
System Integration Environments
Agile Assembly Architecture
Scrum and XP
Effective Agile Retrospectives
The Agile Coach
Rapid RTC
Advanced Roadmaps
Lean Agile Organization
AI Artificial Intelligence
Continuous Planning
IT Operations
Perfection Game
PI Objectives
Lean and Agile Techniques
Limiting Work in Progress
System Archetypes
Large Scale Scrum
Lean Agile Basics
Sprint Iteration
Legacy Code
Lean Budgeting
Process Improvement
Iterative Incremental Development
Agile Techniques
Nexus vs SAFe
Kanban 101
ScrumMaster Tales
Agile Release Planning
Scrum Guide
Sprint Planning
Systems Thinking
Agile Program
Change Management
Entrepreneurial Operating System®
Agile Community
Lean-Agile Budgeting
Releases Using Lean
Software Development
Agile Project Management
Professional Scrum Product Owner
Continuous Integration
Risk Management on Agile Projects
Agile Product Development
Agile Mindset
Agile Testing Practices
Applying Agile Methodology
ALM Tools
Agile Basics
Agile Development
Agile Marketing
Scaled Agile Framework
speed at scale
Risk Management in Kanban
Kaizen Workshop
Agile Project
Scrum Values
Professional Scrum with Kanban
Jira Plans
Games and Exercises
Daily Scrum
Agile for Embedded Systems
Test Driven Development
RTE Role
Pomodoro Technique
Agile Games and Exercises
Kanban Game
Operational Value Stream
Kanban Kickstart Example
Lean Software Development
Agile Release Management
Enterprise DevOps
Agile Israel Events
Agile Contracts Best Practices
Lean-Agile Software Development
Scrum Primer
ART Success
Scrum Master
SAFe DevOps
Agile Israel
Agile Exercises
Principles of Lean-Agile Leadership
Agile Outsourcing
Jira Cloud
Managing Projects
Agile Delivery
Agile Product Ownership
Scrum Master Role
Lean Startup
Agile India
Artificial Intelligence
Development Value Streams
Elastic Leadership
Nexus Integration Team
Introduction to ATDD
Risk-aware Product Development
Program Increment
Nexus and Kanban
Agile in the Enterprise
Jira admin
Lean Agile Leadership
SAFe Release Planning
Software Development Estimation
Implementing SAFe
Manage Budget Creation
Accelerate Value Delivery At Scale
Reading List
Managing Risk on Agile Projects
Lean Agile Management
An Appreciative Retrospective
Kanban Basics
A Kanban System for Software Engineering
What Is Kanban
Coaching Agile Teams
Quality Assurance
Agile Games
lean agile change management
PI Planning
Introduction to Test Driven Development
Value Streams
speed @ scale
Professional Scrum Master
Continuous Delivery
Built-In Quality
Scrum With Kanban
Engineering Practices
Legacy Enterprise
Agile Risk Management
Sprint Retrospectives
Lean and Agile Principles and Practices
Hybrid Work
Portfolio for Jira
Lean Risk Management
Acceptance Test-Driven Development
Product Management
Certified SAFe
System Team
Achieve Business Agility
Continuous Improvement
Implementation of Lean and Agile
The Kanban Method
Nexus and SAFe
Enable registration in settings - general

Contact Us

Request for additional information and prices

AgileSparks Newsletter

Subscribe to our newsletter, and stay updated on the latest Agile news and events

This website uses Cookies to provide a better experience
Shopping cart