Treatment Effect Heterogeneity in Theory and Practice

Instrumental Variables (IV) methods identify internally valid causal effects for individuals whose treatment status is manipulable by the instrument at hand. Inference for other populations requires some sort of homogeneity assumption. This paper outlines a theoretical framework that nests all possible homogeneity assumptions for a causal treatment-effects model with a binary instrument. The framework suggests strategies for using IV estimates for extrapolation, while making it clear that efforts to go from local average treatment effects (LATE) to population average treatment effects are inherently speculative. These ideas are illustrated in an application using sibling-sex composition to estimate the effect of child-bearing on economic and marital outcomes for mothers with two or more children. The application is motivated by welfare reform, which penalizes further childbearing by welfare mothers on the grounds that more children make continued poverty and welfare receipt more likely. The empirical results generally support the notion of reduced labor supply and increased poverty rates as a consequence of additional childbearing, but evidence on the impact of childbearing on marital stability and welfare use is more tenuous. Another interesting finding is that for the sample of teen mothers, LATE is essentially equal to the population average treatment effect.

Impacts of Weather and Time Horizon Selection on Crop Insurance Ratemaking: A Conditional Distribution Approach

An important issue in the agricultural actuarial literature is the extent to which sample period selection affects the accuracy of insurance rating. A conditional Weibull distribution approach is developed which explicitly models the interaction of weather, technology, and other variables on probabilistic yield outcomes to address this issue. Results from an application with an extensive producer-level yield dataset representing commercial-scale Illinois firms suggest that the impact of weather heterogeneity on risk estimation across reasonable samples is likely not as great as is often claimed. The results also suggest that yield risk is decreasing significantly through time, and indicate the presence of trend acceleration. A rating analysis indicates that violations in the risk evolution assumptions of the rating approaches used in the Federal Crop Insurance Program—which implicitly assume increasing yield risk through time when yields trend—result in severely biased rates, with typical overstatements of 200% to 400% for Midwest corn.Conditional Weibull Distribution, Conditional Production Function, Catastrophic Risk Modeling, Sample Selection, Yield Risk, Crop Insurance, Ratemaking, Crop Production/Industries, Risk and Uncertainty,

Notes on an analogue of the Fontaine-Mazur conjecture

We estimate the proportion of function fields satisfying certain conditions which imply a function-field analogue of the Fontaine-Mazur conjecture. As a byproduct, we compute the fraction of abelian varieties (or even Jacobians) over a finite field which have a rational point of order l.Comment: 12 pages; minor revisions according to referees' comment

The Battle to Define the Scope of Attorney-Client Privilege in the Context of Insurance Company Bad Faith: A Judicial War Zone

[Excerpt] The attorney-client privilege is the oldest of the privileges for confidential communications known to the common law. \u27 The privilege is [d]eeply rooted in public policy, and plays a \u27vital role\u27 in the administration of justice. As such, the privilege is traditionally deemed worthy of maximum legal protection \u27 and it remains one of the most carefully guarded privileges and is not readily to be whittled down. The privilege has come under assault in the insurance bad faith context in recent decades resulting in a whittling down of the privilege for insurance companies as a target party. Over the past couple of decades, various courts have rendered significant decisions regarding implied waiver of the privilege in the insurance bad faith context. These courts have seemingly set a minimal threshold for waiver that is the functional equivalent of a per se waiver rule, a rule which is inconsistent with the strength of the protection normally provided the attorney-client privilege in other contexts involving non-target parties. In contrast, Arizona, one of the jurisdictions which previously appeared to create such a per se rule, may be, with recent intermediate court decisions, redefining the battle for the scope of the attorney-client privilege in the insurance bad faith context. The Arizona decisions on this issue serve as a case study regarding the analytic gymnastics courts have engaged in to create implied waiver in the insurance bad faith context. However, these decisions may also set the stage for the judicial combatants. Will the battle result in a return to the more conservative protections of the privilege provided in other contexts or will it end with a broad per se implied waiver in the insurance context? In Part I of this article, the attorney-client privilege is discussed generally, as well as specifically, in the context of insurer bad faith. In Part I.A, a general overview of the attorney-client privilege is presented. In Part I.B, express and implied waiver of the attorney-client privilege are discussed. The courts have disagreed on the general contours of the test to be applied in determining whether an implied waiver of the attorney-client privilege has occurred, and what should be the precise formulation for that determination. The courts have also disagreed as to when a client may be deemed to have injected privileged attorney-client communications into a case, causing an implied waiver. There are three general approaches to determine whether a litigant has impliedly waived the attorney-client privilege. Each of these approaches is discussed. In Part I.C, the article discusses general principles regarding insurance bad faith and how the direct assertion of the advice-of counsel defense results in waiver of the attorney-client privilege in that context. The nature and scope of the advice-of-counsel defense is explored. In Part II, the battle over the changing boundaries of waiver by implication is examined by comparing the case authority supporting expansion versus the development of three published decisions from the courts of Arizona. The discussion starts in Part IIA, where the expansion of waiver by implication is discussed. Part II.B examines a decision from the Arizona Supreme Court which followed the trend of substantial expansion of the waiver-by-implication rule and then examines two subsequent decisions from the Arizona Court of Appeals which have applied the Arizona Supreme Court precedent to reach two very different and arguably contradictory results. The first of these appellate decisions arguably takes the expansion of implied waiver to the next level-a per se rule triggering automatic waiver as a result of defending a bad faith case on a subjective belief of acting in good faith. The second appellate decision, however, takes a step back from the ledge and seeks to limit the prior ruling to its facts rather than creating a per se rule in those circumstances. Part II.C seeks to synthesize and define the battle in Arizona over the scope of implied waiver, discussing the chilling effect continued expansion of implied waiver can have upon the advice that insurance companies seek from counsel and how the recent decision from Arizona may serve as a warm front to thaw the chill that has been in the air for the last two decades

Obliquities of Kepler Stars: Comparison of Single- and Multiple-Transit Systems

The stellar obliquity of a transiting planetary system can be constrained by combining measurements of the star's rotation period, radius, and projected rotational velocity. Here we present a hierarchical Bayesian technique for recovering the obliquity distribution of a population of transiting planetary systems, and apply it to a sample of 70 Kepler Objects of Interest. With ~95% confidence we find that the obliquities of stars with only a single detected transiting planet are systematically larger than those with multiple detected transiting planets. This suggests that a substantial fraction of Kepler's single-transiting systems represent dynamically hotter, less orderly systems than the "pancake-flat" multiple-transiting systems.Comment: 8 pages, 7 figures, accepted to Ap