Gaver, Kenneth M.; Horsky, Dan; Narasimhan, Chakravarthi - In: Marketing Science 7 (1988) 2, pp. 169-186
The sales-marketing mix relationships for brands of a product class are often modelled as a multiple equation system. Whenever sales are expressed as shares, such systems are sum-constrained and therefore singular. Singular systems can be calibrated by deleting one equation from the model and...