Scholarship on social policy has recently emphasised the importance of gradual processes of institutional change. However, conceptual work on the identification of processes such as drift, conversion and layering has not produced clear empirical indicators that distinguish these processes from one another, posing major problems for empirical research. We argue that, in order to improve the validity of its empirical findings, scholarship on gradual change should - and can - pay more attention to issues of measurement and detection. We then contribute to this goal by clearly articulating observable indicators for several mechanisms of gradual institutional change and validating them against extant empirical work on political economy.