Effectiveness of code reviews

Really interesting research article on the impact of various factors on code review effectiveness. The research focuses on a single product:

"analysis of data collected from a (commercial) software project and developers from a single software development company"

The findings should be not new to all of us, but, personally, I always appreciate having data to back experience up.

All the study findings in one chart

The take aways 👇: 

Change size: size negatively affects all outcomes of code review that we consider as an indication of effectiveness. Reviewers are less engaged and provide less feedback. Moreover, the duration is not linearly proportional to the patch size, which may affect the quality of code review.

Number of Teams involved: code reviews involving more teams have lower effectiveness considering duration and participation, but higher effectiveness with respect to the overall comment density. Comment density by reviewer is slightly higher when two teams are involved when compared to reviews involving one or three teams.

Number of Active reviewers: code reviews involving more than one reviewers have lower effectiveness considering the duration. The participation is slightly lower with more active reviewers. Moreover, having more than two active reviewers does not improve the overall comment density and negatively affects the comment density by reviewer.