[Paper Review] Diversity, Productivity, and Growth of Open Source Developer Communities

Qingye Jiang, Young Choon Lee+2 more|arXiv (Cornell University)|Sep 11, 2018

Open Source Software Innovations31 references4 citations

TL;DR

This study analyzes 20 open source projects using git commit data to examine how community diversity, productivity, and growth evolve over time. It finds that high diversity—indicating multiple major contributors—leads to more predictable productivity growth and greater community stability, while low diversity, dominated by a single organization, correlates with less predictable productivity and higher vulnerability to contributor changes.

ABSTRACT

The open source development model has become a paradigm shift from traditional in-house/closed-source software development model, with many successes. Traditionally, open source projects were characterized essentially by their individual volunteer developers. Such tradition has changed significantly with the participation of many organizations in particular. However, there exists a knowledge gap concerning how open source developer communities evolve. In this paper, we present some observations on open source developer communities. In particular, we analyze git repositories of 20 well-known open source projects, with over 3 million commit activities in total. The analysis has been carried out in three respects, productivity, diversity and growth using the Spearman's rank correlation coefficient, diversity index and the Gompertz/logistic curves, respectively. We find out that (a) the Spearman's rank correlation coefficient between active contributors and commit activities reveals how changes in the size of the developer community impacts the productivity of the community; (b) the diversity index of an open source developer community reveals the structure of the community; and (c) the growth of open source developer communities can be described using different phases of growth curves as in many organic matters.

Motivation & Objective

• Understand how the size, diversity, and growth of open source developer communities affect project productivity and sustainability.
• Address the knowledge gap in how open source communities evolve over time, particularly in response to organizational participation.
• Investigate the relationship between community structure (diversity), productivity (commit activity), and growth dynamics.
• Provide empirical evidence on whether community diversity leads to more resilient and scalable open source projects.

Proposed method

• Analyzed git repositories of 20 well-known open source projects with over 3 million commit activities as of December 2015.
• Used Spearman’s rank correlation coefficient to measure the relationship between active contributors and commit activity, assessing productivity scaling with community size.
• Applied a diversity index to quantify the distribution of contributions across organizations, identifying dominance or balance in contributor structure.
• Fitted Gompertz and logistic growth curves to model the growth trajectory of developer communities over time.
• Identified community structure patterns using power law distribution of contributions, consistent with scale-free network characteristics.
• Classified projects based on diversity levels (low, medium, high) to compare productivity and growth stability across structural types.

Experimental results

Research questions

• RQ1 How does the size of an open source developer community affect its productivity, as measured by commit activity?
• RQ2 How can the diversity of contributor organizations in an open source community be quantified, and what impact does it have on community structure and stability?
• RQ3 Can the growth of open source developer communities be modeled using biological growth curves such as Gompertz or logistic functions?
• RQ4 How does diversity influence the predictability and sustainability of productivity as community size increases?
• RQ5 What structural characteristics distinguish high-growth, stable open source communities from those prone to stagnation or collapse?

Key findings

• A high Spearman’s rank correlation coefficient between active contributors and commit activity indicates that productivity scales predictably with community size, especially in diverse communities.
• Communities with low diversity are dominated by a single organization, while high diversity indicates multiple major contributors with roughly equal contribution shares.
• Highly diverse communities exhibit greater stability, as their productivity remains predictable even when individual contributors or organizations leave.
• The growth of open source communities follows S-shaped curves, best modeled by Gompertz or logistic functions, indicating distinct phases of rapid growth, plateau, and maturity.
• Communities with high diversity tend to remain in the exponential growth phase longer, due to reduced dependency on any single contributor or organization.
• Projects dominated by a single organization show lower correlation between size and productivity, indicating less scalable or predictable development patterns.