What exactly is the economic rationale for that damage estimate?

An economic expert was asked to estimate the damages associated with the improper use of a trademark. The trademark had been sold to a competitor, but the use of the trademark in annual distributors’ catalogs inadvertently had not been excluded from the manufacturer’s listings. The plaintiff sought economic damages, arguing that the misuse of the trademark injured the plaintiff’s sales while enhancing the defendant’s sales of it new product line. The plaintiff’s economic expert, in estimating its alleged lost sales, made the argument that one-third of the defendant’s sales of its new product “belonged” to the plaintiff as a direct result of the misuse of the plaintiff’s trademark. There was no foundation for the one-third proportion, and the expert provided no justification for the figure, other than its seemed “likely” that this was the appropriate proportion. Needless to say, the calculation of alleged damages was not convincing.