Even before the start of their second year in office, commentators were already reading the tea leaves on Samuel A. Alito, Jr. and John G. Roberts, Jr. According to the prominent legal scholar Erwin Chemerinsky, the two new justices “were every bit as conservative as conservatives had hoped and progressives had feared. [Their] willingness to overrule decades-old precedents certainly gives a sense that major changes are likely ahead in constitutional law in the years to come.” Chemerinsky was hardly alone; similar forecasts appeared on the editorial pages of newspapers as ideological disparate as the Wall Street Journal and the New York Times, as well as hundreds, if not thousands, of blogs across the country. Forecasting of this sort—a veritable cottage industry each time a new justice completes a term or two of service—may seem harmless enough and sufficiently divorced from the concerns of empirical legal studies to ignore. Nonetheless, the entire enterprise rests on a strong empirical assumption, which, in fact, has important implications for systematic scholarship: that one can draw high-quality inferences about the justices’ long-term ideological tendencies from their first few terms in office. Is this a plausible assumption? Unfortunately, and despite decades of study, we cannot offer a conclusive answer. To some, most notably Hagle, reliance on initial voting records to predict future behavior borders on the absurd. Most justices, he empirically demonstrated, manifest unstable behavior in their “freshman” year relative to the balance of their career. To other scholars, most recently Shipan, predictions based on the first term are not particularly troubling. The instability identified by Hagle, they say, appears insufficiently widespread to be “considered a general phenomenon.” In between comes work by Wood et al., which found that roughly half the justices under analysis experienced “acclimation” effects. On the perils of drawing inferences about Supreme Court justices from their first few years of service