Fact, Fiction, and the Size Effect
用90多年美国数据检验规模效应，发现纯规模效应不存在，可能是数据错误和风险流动性调整不足所致，对理解市场异象和投资策略有参考价值。
In the earliest days of empirical work in academic finance, the size effect was the first market anomaly to challenge the standard asset pricing model and prompt debates about market efficiency. The notion that small stocks have higher average returns than large stocks, even after risk adjustment, was a path-breaking discovery, and for decades it has been taken as an unwavering fact of financial markets. In practice, the discovery of the size effect fueled a crowd of small-cap indexes and active funds to the point that the investment landscape is now segmented into large and small stock universes. However, despite its long and illustrious history in academia and its commonplace acceptance in practice, there is still confusion and debate about the size effect. We examine many claims about the size effect and aim to clarify some of the misunderstanding surrounding it by performing simple tests using publicly available data. For one, using 90+ years of U.S. data, there is no evidence of a pure size effect; moreover, it may not have existed in the first place, if not for data errors and insufficient adjustments for risk and liquidity. <b>TOPICS:</b>Portfolio theory, analysis of individual factors/risk premia