Much of this corresponds to my personal experience over the years, and is hardly that controversial. However, despite sufficient evidence to the contrary, insiders’ disclosures are still being routinely used for simultaneous asset selection and strategy validation. Which, of course, sets an investor for absorbing the risks inherent in any and all biases present in the insiders’ activities.
In their March 2016 paper, titled “Trading Skill: Evidence from Trades of Corporate Insiders in Their Personal Portfolios”, Ben-David, Itzhak and Birru, Justin and Rossi, Andrea, (NBER Working Paper No. w22115: http://ssrn.com/abstract=2755387) looked at “trading patterns of corporate insiders in their own personal portfolios” across a large dataset from a retail discount broker. The authors “…show that insiders overweight firms from their own industry. Furthermore, insiders earn substantial abnormal returns only on stocks from their industry, especially obscure stocks (small, low analyst coverage, high volatility).” In other words, insiders returns are not distinguishable from liquidity risk premium, which makes insiders-strategy alpha potentially as dumb as blind ‘long lowest percentile returns’ strategy (which induces extreme bias toward bankruptcy-prone names).
The authors also “… find no evidence that corporate insiders use private information and conclude that insiders have an informational advantage in trading stocks from their own industry over outsiders to the industry.”
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Which means that using insiders’ disclosures requires (1) correcting for proximity of insider’s own firm to the specific sub-sector and firm the insider is trading in; (2) using a diversified base of insiders to be tracked; and (3) systemically rebalance the portfolio to avoid concentration bias in the stocks with low liquidity and smaller cap (keep in mind that this applies to both portfolio strategy, and portfolio trading risks).
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