Business process standardization is the activity of unifying different variants of a family of business processes. While the positive effects of business process standardization are well-described, it is often undesirable to fully unify different variants due to cultural, legal, or operational reasons. Consequently, a decision has to be made about the extent to which a family of business processes should be standardized. However, little is known about the factors that drive that decision. This paper fills that gap, by presenting factors that drive the extent to which business processes can be standardized, performance properties that are influenced by business process standardization, and relations between these concepts.