Data Analysis: Once we manually examine the review samples, we calculate the reviewing time of the review samples. Reviewing time is the time difference from the time that a code change has been submitted to the time that the code changes are approved or abandoned. We then compare the distributions of the reviewing time between reviews with and without code-reviewer assignment problem using beanplots [31]. Beanplots are boxplots in which the vertical curves summarize the distributions of different data set. The horizontal lines indicate the average (median) reviewing time (days). We use a Mann-Whitney’s U test (α = 0.05), which is a non-parametric test, to statistically determine the difference of the reviewing time distributions. Since reviewing time can be influenced by patch size [15, 19], we divide the reviewing time by the patch size before performing a statistical test.