Unlike Arrow’s result for process innovations, the gain from a product innovation can be larger to a secure monopolist than to a rivalrous …rm that would face competition from independent sellers of the old product. A monopolist incurs pro…t diversion from its old good but may gain more than a rivalrous …rm on the new good by coordinating the prices. In a Hotelling framework, we …nd simple cond...

in the real world there are groups which composed of independent units. the conventional data envelopment analysis(dea) model treats groups as units, ignoring the operation of individual units within each group.the current paper, investigates parallel system network approach proposed by kao and modifies it. as modied kao' model is more eligible to recognize ecient groups, a new ranking m...