Modelling market shares by segments using volatility

This paper presents the results of market share modelling for individual segments of the UK tea market using scanner panel data. The study is novel in its introduction of the use of volatility as one of the bases for segmentation, others being usage, loyalty or switching between product types and product forms. The segmentation is undertaken on an a priori, quasi-experimental basis, allowing nested tests of constancy of elasticities across segments. The estimated equations (using seemingly unrelated regressions) benefit from extensive specification, including four diff erent forms for the price variable, four variables for promotion, and six for product characteristic, distribution and macroeconomic variables. Tests for the constancy of the parameters across segments show the segmentation to be successful.