An open market is a subset of a larger equity market, composed of a certain fixed number of top-capitalization stocks. Though the number of stocks in the open market is fixed, their composition changes over time, as each company's rank by market capitalization fluctuates. When one is allowed to invest also in a money market, an open market resembles the entire “closed” equity market in the sense that the market viability (lack of arbitrage) is equivalent to the existence of a numéraire portfolio (which cannot be outperformed). When access to the money market is prohibited, the class of portfolios shrinks significantly in open markets; in such a setting, we discuss the Capital Asset Pricing Model, how to construct functionally generated portfolios, and the concept of universal portfolio.

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公开市场

公开市场是较大股票市场的一个子集，由一定数量的大市值股票组成。尽管公开市场上的股票数量是固定的，但它们的构成会随着时间的推移而变化，因为每家公司的市值排名都会波动。当一个人也被允许投资于货币市场时，一个公开市场类似于整个“封闭”股票市场，因为市场可行性（缺乏套利）相当于存在一个数字投资组合（不能被超越） . 当禁止进入货币市场时，公开市场中的投资组合类别会显着缩小；在这种情况下，我们将讨论资本资产定价模型、如何构建功能生成的投资组合以及通用投资组合的概念。