We develop a two-country model of endogenous investment in process innovation by a manufacturer facing competition from parallel imports (PI). We find that the distortions associated with PI inhibit innovation. However, the difference between the manufacturer's expected profits under successful and failed innovation is U-shaped in the cost of engaging in PI. Thus, the reduction in R&D investment depends on both legality of PI and transport costs. The reduction in innovation could harm global welfare, depending on whether the manufacturer was deterring PI with a high wholesale price. If so, banning such trade would raise expected welfare.

In this paper, we develop a vertically differentiated duopoly model where a high-quality producer competes against a low-quality producer, a la Cournot competition. The high-quality firm has both a new technology and an obsolescent technology. After first deciding whether to license, the firm then chooses which of the two technologies to license. We show that, irrespective of the licensing contract, licensing the new technology is always superior to licensing the obsolescent technology. This finding poses a sharp contrast to the conventional wisdom.

This paper incorporates a durable-good monopoly model and re-examines the argument on licensing contracts. It shows that, from the perspective of the non-producing patent holder, the optimal licensing contract depends on the nature and the degree of the innovations. Specifically, for small cost-reducing or quality-improving innovations, charging a royalty is optimal. For large costreducing or quality-improving innovations, licensing by means of a fee and a royalty is superior to using either alone. However, for the case of horizontal product innovations, using a fee contract is optimal.

In this paper, we develop a differentiated duopoly model with endogenous cost-reducing R&D and review the argument on welfare effect of price and quantity competition in the presence of technology licensing. We show that the standard conclusion on duopoly (Singh and Vives, 1984) can be completely reversed. Cournot competition induces lower R&D investment than Bertrand competition does. Moreover, Cournot competition leads to lower prices, lower industry profit, higher consumer surplus and higher social welfare than Bertrand competition.

文章考察Stackelberg竞争条件下的最佳福利关税与最大收入关税。分析表明，最佳福利关税与最大收入关税的相对大小主要取决于产品之间的相互关系和国内外企业的成本差异。当产品是互补品时，最佳福利关税总是小于最大收入关税；当产品是替代品时，最佳福利关税与最大收入关税的关系，既取决于产品间的替代程度又取决于国内外企业间的成本差异。产品的替代程度较弱时，最大收入关税总是大于最佳福利关税；产品的替代程度较强时，若国内外厂商间的成本差异越小，则最佳福利关税越有可能超过最大收入关税。