The asymptotic relative efficiencies of tests and the derivatives of their power functions

Abstract

For comparing two consistent tests of a simple null hypothesis H ₀ : θ = θ₀ against a given alternative hypothesis H ₀ : θ = θ₁, the measure most frequently used is the asymptotic relative efficiency (ARE), due to Pitman (1948). The ARE is defined as the limit of the reciprocal of the ratio of sample sizes required to attain the same power. The limit is taken as sample sizes tend to infinity and simultaneously θ₁ → θ₀, this being necessary to keep the powers of the tests bounded away from 1.     

Does the forward premium puzzle disappear over the horizon?

This paper provides the first comprehensive study of the horizon effect in tests of the forward rate unbiasedness hypothesis. It estimates Fama regressions employing 1-month through to 10-year horizon data for the five most heavily traded US dollar currency pairs pre-crisis 1980–2006. In contrast with extant studies, it fully deals with the econometric problems of long horizon regressions by means of a novel heteroskedastic- and autocorrelation-consistent bootstrap. The regression results confirm a clear horizon effect in that the slope coefficient approaches unity as the forward contract maturity is extended. The puzzle disappears at the 3-year horizon and beyond for all currencies.     

Asymmetric information,adverse selection,and the pricing of CMBS

We demonstrate that asymmetric information between sellers (loan originators) and purchasers (investors and securities issuers) of commercial mortgages gives rise to a standard lemons problem, whereby portfolio lenders use private information to liquidate lower quality loans in commercial mortgage-backed securities (CMBS) markets. Conduit lenders, who originate loans for direct sale into securitization markets, mitigate problems of asymmetric information and adverse selection in loan sales. Our theory provides an explanation for the pricing puzzle observed in CMBS markets, whereby conduit CMBS loans are priced higher than portfolio loans, despite widespread belief that conduit loans are originated at lower quality. Consistent with theoretical predictions of a lemons discount, our empirical analysis of 141 CMBS deals and 16,760 CMBS loans shows that, after controlling for observable determinants of loan pricing, conduit loans enjoyed a 34 basis points pricing advantage over portfolio loans in the CMBS market.     

Mergers and marginal costs: New evidence on hospital buyer power

We estimate the effects of hospital mergers, using detailed data containing medical supply transactions (representing 23% of operating costs) from a sample of US hospitals, 2009–2015. Pre‐merger price variation across hospitals (Gini coefficient 7%) suggests significant opportunities for cost decreases. However, we observe limited evidence of actual savings. In this retrospective study, targets realized 1.9% savings; acquirers realized no significant savings. Examining treatment effect heterogeneity to shed light on theories of “buyer power,” we find that savings, when they occur, tend to be local, and potential benefits of savings may be offset by managerial costs of merging.