De-mystifying the Inconvenient Truth : Does Ex Post Moral Hazard Indeed Exist in Korean Private Health Insurance Market?

There have been heated debates on whether private health insurance creates moral hazard effects. Despite its importance, however, the moral hazard problem of private health insurance is still controversial and understudied. To empirically examine whether or not moral hazard exists in the Korean private health insurance market, we employed two-stage regression for endogeneity control and the Heckman two-step procedure for sample selection bias control, which are expected to produce consistent estimates. All estimation results do not allow us to detect the presence of the moral hazard effects and imply that people hold private health insurance simply as “safety net”.Private Health Insurance, Moral Hazard, Endogeneity, Sample Selection Bias

The Effect of Patient's Asymmetric Information Problem on Medical Care Utilization with Consideration of a Patient's Ex-ante Health Status

Even if a patient's access to health information has been enhanced, a patient still doesn't have enough ability to utilize it. Therefore, a doctor's effort to sincerely communicate with a patient might affect the patient's use of medical care. This paper builds up the empirical model and found the effect of a doctor's effort on patient's medical care use was significant and according to the ex-ante health status of a patient, a doctor's effort influenced a patient's medical care use in different way.asymmetry of information between doctor and patient, patient's medical care use, doctor's effort to effectively communicate with patients, patient's ex-ante health status

Optimal Brownian Stopping between radially symmetric marginals in general dimensions

Given an initial (resp., terminal) probability measure $\mu$ (resp., $\nu$) on $\mathbb{R}^d$, we characterize those optimal stopping times $\tau$ that maximize or minimize the functional $\mathbb{E} |B_0 - B_\tau|^{\alpha}$, $\alpha > 0$, where $(B_t)_t$ is Brownian motion with initial law $B_0\sim \mu$ and with final distribution --once stopped at $\tau$-- equal to $B_\tau\sim \nu$. The existence of such stopping times is guaranteed by Skorohod-type embeddings of probability measures in "subharmoic order" into Brownian motion. This problem is equivalent to an optimal mass transport problem with certain constraints, namely the optimal subharmonic martingale transport. Under the assumption of radial symmetry on $\mu$ and $\nu$, we show that the optimal stopping time is a hitting time of a suitable barrier, hence is non-randomized and is unique

Early-type Host Galaxies of Type Ia Supernovae. I. Evidence for Downsizing

Type Ia supernova (SN Ia) cosmology provides the most direct evidence for the presence of dark energy. This result is based on the assumption that the look-back time evolution of SN Ia luminosity, after light-curve corrections, would be negligible. Recent studies show, however, that the Hubble residual (HR) of SN Ia is correlated with the mass and morphology of host galaxies, implying the possible dependence of SN Ia luminosity on host galaxy properties. In order to investigate this more directly, we have initiated spectroscopic survey for the early-type host galaxies, for which population age and metallicity can be more reliably determined from the absorption lines. As the first paper of the series, here we present the results from high signal-to-noise ratio (>100 per pixel) spectra for 27 nearby host galaxies in the southern hemisphere. For the first time in host galaxy studies, we find a significant (~3.9sigma) correlation between host galaxy mass (velocity dispersion) and population age, which is consistent with the "downsizing" trend among non-host early-type galaxies. This result is rather insensitive to the choice of population synthesis models. Since we find no correlation with metallicity, our result suggests that stellar population age is mainly responsible for the relation between host mass and HR. If confirmed, this would imply that the luminosity evolution plays a major role in the systematic uncertainties of SN Ia cosmology.Comment: Accepted for publication in ApJ