The most straightforward area in word formation where corpora can be used is the study of productivity. We compare three approaches to the study of productivity, concentrating on what Corbin (1987) calls rentabilité (‘profitability’). Baayen (1992) calculates productivity in this sense on the basis of hapaxes in a corpus. In Chomskyan linguistics, the emphasis is rather on disponibilité (‘availability’), because it is a property of the competence. Štekauer (1998) sharply distinguishes productivity and frequency and defines the former so that corpus use is not essential. In comparing the approaches, we argue that rentabilité is worth studying, but that Baayen’s approach depends on a notion of language where language use is taken to be prior to the language system. Štekauer’s approach offers a promising basis for reconciling individual and speech community perspectives on language. A systematic use of corpora would strengthen the results obtained on productivity.