The U.S. Constitution guarantees criminal defendants the right to an impartial jury selected from a jury pool that reflects the demographic composition of the geographic community served by the court. Yet there is little consensus in case law from state and federal courts about the most appropriate method of measuring demographic representation or the degree of underrepresentation that would violate the fair-cross-section requirement. Although the U.S. Supreme Court recently addressed these issues for the first time since Duren v. Missouri, its opinion in Berghuis v. Smith did little to settle the questions. In the present article, the authors use demographic information from the U.S. Census Bureau and information about jury operations in state courts from the National Center for State Courts to estimate the potential impact of competing proposals about how to measure demographic representation at different threshold levels of constitutional tolerance. Given the demographic composition of counties in the United States and the size of the jury pool in most courts, the authors find that a bright-line rule using either of the two most common measures of representation (absolute disparity and comparative disparity) would create “safe harbors” in which the courts in a majority of jurisdictions across the country would become effectively immune from fair-cross-section challenges.