In this paper we present an empirical study of formal specifications written in the Event-B language. Our study is exploratory, since it is the first study of its kind, and we formulate metrics for Event-B specifications which quantify the diversity of such specifications in practice. We pay particular attention to refinement as this is one of the most notable features of Event-B. However, Event-B is less well-equipped with other standardised modularisation constructs, and we investigate the impact of this by detecting and analysing specification clones at different levels. We describe our algorithm used to identify clones at the machine, context and event level, and present results from an analysis of a large corpus of Event-B specifications. Our study contributes to furthering research into the area of metrics and modularisation in Event-B.