Refactoring is one of the means of managing technical debt and maintaining a healthy software structure through enforcing best design practices, or coping with design defects. Previous refactoring surveys have shown that these code restructurings are mainly executed by developers who have sufficient knowledge of the system's design, and disposing of leadership roles in their development teams. However, these surveys were mainly limited to specific projects and companies. In this paper, we explore the generalizability of the previous results though analyzing 800 open-source projects. We mine their refactoring activities, and we identify their corresponding contributors. Then, we associate an expertise score to each contributor in order to test the hypothesis of whether developers with higher scores tend to perform a higher number of refactoring operations. We found that (1) although refactoring is not restricted to a subset of developers, those with higher experiences score tend to perform more refactorings than others; (2) our qualitative analysis of three randomly sampled projects show that the developers who are responsible for the majority of refactoring activities are typically on advanced positions in their development teams, demonstrating their extensive knowledge of the design of the systems they contribute to.