We model the optimal behaviour of a multiproduct monopolist investing both in process and in product innovation in a dynamic setting. Product innovation reduces the degree of substitutability between any two varieties. First, we find that R&D efforts increase in both directions as the number of...

In markets where product quality is important, more than one characteristic is usually necessary to define product quality and the amelioration of the goods characteristics is usually costly. Then, properties of production technologies, in particular if they exhibit economies or diseconomies of...