Perfect completion: there is a competition to the point of marginal cost (price=marginal cost)
competition forces innovation (differentiate) , while cartelization let firm reduce risk.
while cartelization make high profits at expense of customers
Ban on Cartel (setting high prices jointly)
Merge Control
什么样的情况会促使Cartel 的形成？
1. 价格和销售量非常容易预估。
2. 市场非常好把控（技术，需求，成本）
3. 行业早前出现过Cartel
Abuse Control
如何测算一家公司在市场是否存在霸权？
1. 产品角度： 测算价格弹性，产品交叉弹性。
2. market power: 测算市场集中度
HHI 指数 C=汇总（市场份额）^2
HHI <1000, acceptable
1000<HHI<1800 moderate to high
HHI>1800 highly concentrated
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