The objective of this study was to assess the costs of imperfect interoperability to the U.S. automotive supply chain and to describe the sources of these costs. By understanding the sources and magnitude of inefficiencies caused by interoperability problems, NIST can better determine the potential impact of its programs and focus them to maximize program effectiveness. This study estimates that imperfect interoperability imposes at least $1 billion per year on the members of the U.S. automotive supply chain. By far, the greatest component of these costs is the resources devoted to repairing or reentering data files that are not usable for downstream applications. This estimate is conservative because we could not quantify all sources of interoperability costs.