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.

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.

We study the dependence of incentives for product innovation on the presence, or absence, of parallel trade. The common assertion is that the presence of parallel trade lowers the incentive for product innovation. Our results support this assertion for some parameter values. However, there are cases in which the presence of parallel trade increases research intensity. For this to occur the innovating firm must already produce and export another good. Further, the new good and the old must be close substitutes and have different transportation costs.

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 location-quantity model of mixed oligopoly where a welfare-maximizing firm competes against multi-store profit-maximizing firms. We show that agglomeration of private firms occurs in a circular market regardless of the number of stores of the public firm. Whether or not equidistant location patterns exist depends crucially on the number of stores of the public firm. If the public firm has a single store, then nonequidistant location pattern arises. However, if the public firm has two stores, then under the assumption of quasi-symmetric location patterns, equidistant location pattern is the outcome in equilibrium.

一个拥有买方势力的连锁企业在多个相互分割的零售市场，分别与一个没有买方势力的地方企业进行Stackelberg竞争，其中连锁企业是一个部分追求利润、部分追求社会福利的国有企业，地方企业是一个完全追逐利润的私营企业。研究表明：无论连锁企业是否先行进入市场，买方势力的存在都损害了地方企业与上游厂商的利益，提高了连锁企业的利润，并惠及消费者乃至整个社会。

一个具有购买势力的连锁企业在多个地方市场上分别与一个没有购买势力的地方企业进行Stackelberg竞争，其中连锁企业是纯粹追求利润的私营企业，而地方企业是部分追求利润、部分追求社会福利的国有企业。我们分析了连锁企业的购买势力对企业利润、消费者剩余以及社会福利等的影响。研究表明：连锁企业的利润随着其购买势力的增大而增加，但是，地方企业的利润与上游厂商的利润取决于地方企业国有股的比重和连锁企业购买势力的大小；购买势力的存在降低了消费者剩余、产业利润和整个社会的福利水平。

基于一个具有购买势力的连锁企业在若干个相互分割的市场上分别与一个没有购买势力的地方企业进行Cournot 竞争的经济学模型，我们分别讨论了连锁企业是私营企业和部分国有企业时，购买势力对企业利润、消费者剩余以及社会福利的影响。研究表明：当连锁企业是私营企业时，随着其购买势力的增强，其企业利润不断增加，消费者剩余及社会福利不断降低，而上游企业与地方企业的利润变动则取决于地方企业国有股的比重和连锁企业购买势力的大小;当连锁企业是部分国有企业时，随着连锁企业购买势力的增大，连锁企业的利润、消费者剩余以及社会福利会持续升高，而上游企业与地方企业的利润持续降低。

借助于一个上下游模型，对跨国公司、产业链和企业的购买势力对消费者利益和社会福利的影响进行研究，可以得出如下结论：第一，无论是国资企业还是外资企业先行进入市场，也不管是哪个企业拥有购买势力，企业购买势力的增强都会降低上游企业的利润。第二，无论上下游企业是否组成产业联盟，如果连锁企业是国资企业，那么其购买势力的增加可以提高消费者剩余和社会福利；但是，如果连锁企业是外资企业，那么其购买势力的提高必然会损害消费者利益和社会福利。第三，无论上游企业是否是国资企业，如果下游的国资企业与之缔结产业联盟，都会改善社会福利。