An empirical study of clone density evolution and developer cloning tendency

Code clones commonly occur during software evolution. They impact the effort of software development and maintenance, and therefore they need to be monitored. We present a large-scale empirical study (237 open-source Java projects maintained by 500 individuals) that investigates how the number of clones changes throughout software evolution, as well as the tendency of individual developers to introduce clones. Our results will set a point-of-reference against which development teams can compare and, if needed, adjust.