1. 背景
empirical: 2000.10-2007.10, video game monthly sale
2. 目的
to understand the role of vertical integration in video game productionand eventually video game demand
3. 结论
vertically integrated games produce higher revenues, sell more units and sell at higher prices
most of the difference in performance comes from better release period and marketing strategies that soften competition（也可能是消除 contractual frictions in video game production）
integrated video games are inherently worse than independent games，——outsourcing innovation seems to be the way to conduct
research and other uncertain process that may drive costs up too high
exclusivity is associated with lower demand (和之前研究一致)
之前的研究是网络效应对平台需求和竞争的影响，现在研究垂直整合的影响，可是垂直整合不会带来网络效应的扩大么？——Had network effects been absent, these findings seem to indicate that this industry would be less integrated and more atomized than it is currently
