Descriptive adequacy of the S-curve model in diachronic studies of language change

The S-shaped curve is typically used to model the diffusion of linguistic change across time. This paper looks at the degree to which the model applies to empirical real-time data of some time-depth. An S-shaped curve is commonly attested in the quantitative studies discussed, but it is not the only pattern that emerges from systematic analyses. To put the model and its descriptive adequacy into perspective, I consider both typical cases and exceptions to them, notably change reversals. I also draw attention to the level of analytic detail that has a major role to play in empirical research into processes of language change and their outcomes.