Do developers discuss design?

Design is often raised in the literature as important to attaining various properties and characteristics in a software system. At least for open-source projects, it can be hard to find evidence of ongoing design work in the technical artifacts produced as part of the development. Although developers usually do not produce specific design documents, they do communicate about design in different ways. In this paper, we provide quantitative evidence that developers address design through discussions in commits, issues, and pull requests. To achieve this, we built a discussions' classifier and automatically labeled 102,122 discussions from 77 projects. Based on this data, we make four observations about the projects: i) on average, 25% of the discussions in a project are about design; ii) on average, 26% of developers contribute to at least one design discussion; iii) only 1% of the developers contribute to more than 15% of the discussions in a project; and iv) these few developers who contribute to a broad range of design discussions are also the top committers in a project.