Building parable economies embedding econometricians, we view alternative estimators (Instrumental variables, fuzzy regression discontinuity, natural experiments, OLS, event studies) from the perspective of privately informed decision-makers, e.g., CFOs. Instrumental variable estimates can be misleading since randomization through observable instruments eliminates signal content arising from discretion. If the goal is informing discretionary decisions, rather than predicting outcomes after forced/mistaken actions, instrumentation is problematic, whereas OLS or event studies can be sufficient. The analysis shows that the utility of alternative estimators hinges upon often neglected assumptions about agent/econometrician information sets, as distinct from exclusion restrictions. We recommend parable economy estimation before real-world IV estimation.

What determines securitization levels, and should they be regulated? To address these questions we develop a model where originators can exert unobservable effort to increase expected asset quality, subsequently having private information regarding quality when selling ABS to rational investors. Absent regulation, originators may signal positive information via junior retentions or commonly adopt low retentions if funding value and price informativeness are high. Effort incentives are below first‐best absent regulation. Optimal regulation promoting originator effort entails a menu of junior retentions or one junior retention with size decreasing in price informativeness. Zero retentions and opacity are optimal among regulations inducing zero effort.

We derive analytical relationships between shock responses and theory‐implied causal effects (comparative statics) in dynamic settings with linear profits and linear‐quadratic stock accumulation costs. For permanent profitability shocks, responses can have incorrect signs, undershoot, or overshoot depending on the size and sign of realized changes. For profitability shocks that are i.i.d., uniformly distributed, binary, or unanticipated and temporary, there is attenuation bias, which exceeds 50% under plausible parameterizations. We derive a novel sufficient condition for profitability shock responses to equal causal effects: martingale profitability. We establish a battery of sufficient conditions for correct sign estimation, including stochastic monotonicity. Simple extrapolation/error correction formulas are presented.