Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Volunteer-based open-source production has become a significant new model for the organization of software development. Economics often pictures this phenomenon as a case of signalling: individuals engage in the volunteer programming of open-source software (OSS) as a labour-market signal resulting in a wage premium. Yet, this explanation could so far not be empirically tested. This article fills this gap by estimating an upper-bound composite wage premium of voluntary OSS contributions and by separating the potential signalling effect of OSS engagement from other effects. Although some 70% of OSS contributors believe that OSS involvement benefits their careers, we find no actual labour-market premium for OSS engagement. The presence of other motives, such as fun of play or altruism, renders OSS contributions too noisy to function as a signal.