第二篇在sciencedirect上没有pdf下载，原因是文章发表的时间太早，没有收录

Diversity and quality of information products in a monopolistically competitive industry

science direct 上有pdf，我的用户权限不够。

这是链接http://www.sciencedirect.com/science/article/B6V8J-45JKKFY-3/2/23fb4349d9f729e687f4d3ed030be0aa

请大家帮忙一下。万分感谢。

http://www.sciencedirect.com/science/article/B6V8J-45JKKFY-3/2/23fb4349d9f729e687f4d3ed030be0aa
上面链接只能看到摘要，没有提供pdf下载

下面是摘要：

Abstract

Producers of information products decide how much to invest in the ‘first copy’, a choice which determines product quality in economic terms. In this paper, we investigate equilibrium tradeoffs between quality and diversity (or variety) of information products in the framework of Steven Salop's monopolistically competitive model of circular product space. Specifically, we extend Salop's case of linear price support with fixed setup costs to consider three other regimes: non-price support with fixed setup costs, then price and non-price support with variable setup costs. Employing a utility function linear in price and multiplicative in quality, we find that when setup investments can vary, firms have a tendency to underinvest, and that there is an even greater tendency for the industry to overproduce variety relative to the welfare optimum than in Salop's original model. We also find that a conversion from non-price support (e.g., the conversion from advertiser to pay supported television) does not necessarily increase variety but may only lead to higher investment levels, and may or may not increase aggregate consumer welfare.