Our study examines the imitation behavior of UK automobile manufacturers from 1894 to 1981 and supports previous studies on interorganizational imitation by showing that manufacturers tend to imitate other manufacturers that are similar. We also find that the degree of confidence manufacturers have in their imitating behavior affects the intensity of that behavior, where an organization’s confidence is determined by the variance of the routines used by its reference group and the number of firms in the reference group. Our results show that (1) manufacturers whose reference groups showed large variance in niche-width changes during the previous year are less likely to imitate (the mean of) those changes, (2) manufacturers who have large reference groups are more likely to imitate the changes, and (3) the negative effect of variance on the imitating behavior is strengthened as the number of reference organizations increases.