Instrumental variables (IVs) and control variables are frequently used to assist researchers in investigating endogenous treatment effects. When used together, their identities are typically assumed to be known. However, in many practical situations, one is faced with a large and mixed set of covariates, some of which can serve as excluded IVs, some can serve as control variables, whereas others should be discarded from the model. It is often not possible to classify them based on economic theory alone. This paper proposes a data-driven method to classify a large (increasing with sample size) set of covariates into excluded IVs, controls, and noise to be discarded. The resulting IV estimator is shown to have the oracle property (to have the same first-order asymptotic distribution as the IV estimator, assuming the true classification is known).

We study the impact of CEO early-life disaster experience on stock price crash risk. Using a longitudinal sample of U.S. firms, we document that firms led by CEOs with early-life disaster experience have higher stock price crash risk. Our findings are consistent with CEOs who experienced early-life disasters being more risk tolerant, and thus more willing to accept the risks associated with bad news hoarding, engendering formation of stock price crashes. In cross-sectional analyses, we find that the effect of CEO disaster experience is amplified when a CEO has greater equity compensation-based incentives and power over corporate board to hoard bad news. Reinforcing bad news hoarding narrative, we also find that stocks of the firms led by CEOs with early-life disaster experience exhibit stronger asymmetric response to bad versus good news disclosures and are more likely to experience crashes accompanied by breaks in the strings of uninterrupted earnings increases. Further, consistent with early-life disaster experience making CEOs more risk tolerant, we find that firms led by CEOs with early-life disaster experience tend to have higher cash-flow volatility and stock return volatility. Evidence from supplemental analysis suggests that the impact of CEO early-life disaster experience on crash risk varies in a curvilinear manner with the severity of disaster.