Does the duplication of viewing law apply to radio listening?

Purpose There has been long‐standing interest in the duplication of audience between media vehicles, starting with work by Agostini and later developed by Goodhardt, Ehrenberg and Collins into the “duplication of viewing law”. The aim of this paper is to further extend duplication analysis to radio listening. As radio markets are believed to have many partitions, the paper considers whether an un‐partitioned duplication analysis provides an adequate description of market structure. Design/methodology/approach The paper reports the results of a weekly radio diary with 1,129 responses in a regional New Zealand radio market. This data has special characteristics suitable for this research: the market has experienced rapid expansion in station numbers with substantial attempts at format segmentation, providing a strong test of the un‐partitioned nature of the duplication analysis; use of a single regional market avoids the aggregation bias inherent in national data; use of primary research allows the inclusion of non‐commercial stations, which are not included in syndicated radio research in this market. Findings Duplication of listening does broadly follow the duplication of viewing law. Contrary to industry belief, most of the deviations from a mass market are not due to micro‐formats (e.g. classic rock) but rather are explained by a broad partitioning of the market between “talk” and “music” segments, although the paper also identifies a unique station that still deviates from its parent partition. Research limitations/implications The duplication of listening law does hold for this market, showing that radio stations compete largely on the basis of cumulative audience. However, it also provides a tool for identifying partitions and benchmarking station performance within this broad market structure. Future research could consider demographic or psychographic correlates of market partitions, alternative methods of purchase‐based segmentation such as nested logit, latent segmentation and Hendry analysis, and breaking duplication analysis down from weekly level to dayparts. Practical implications Station and network managers can apply this methodology to identify partitions and benchmark brand performance in their own markets. They should expect to usually compete on the basis of cumulative audience rather than station loyalty, as customer loyalty tends to be a feature of the partition rather than the station. Media planners should also be aware of the duplication of listening law when designing media schedules: greater frequency can be achieved by choosing a set of stations with high duplications (generally higher share stations); greater reach can be achieved by including some smaller stations with low duplications. Originality/value This is the first application of duplication analysis to radio audiences, and the confirmation of the law goes against practitioner expectations. It is also a rare example of how duplication analysis can be used to identify not just segments, but also individually unique stations. Therefore, while this research disconfirms prior expectations it also provides a new tool for practical segmentation of radio markets.