Rates of street crime have dropped substantially over the past several decades, but important nuances of this decline are underappreciated and the reasons for it remain unclear. We suggest that the narrow conception of change adopted within criminology has hindered the field's capacity to develop a stronger scientific understanding of crime trends. Criminology has focused heavily on within-person changes in crime, devoting comparatively little attention to changes in aggregate crime rates. In this review, we make a case for integrating research on crime trends into the core of criminology. After describing the late twentieth century crime drop, we present a conceptual framework that situates the study of crime trends in the criminological theoretical literature and illuminates several unresolved questions central to criminological inquiry. We then highlight major shortcomings of current empirical approaches and outline several methodological improvements that would enhance our capacity to describe and explain crime trends.