Markov Aging Process and Phase-Type Law of Mortality

Abstract

In this article, we propose a finite-state Markov process with one absorbing state to model human mortality. A health index called physiological age is introduced and modeled by the Markov process. Under this model the time of death follows a phase-type distribution. The model possesses many desirable analytical properties useful for mortality analysis. Closed-form expressions are available for many quantities of interest including the conditional survival probabilities of the time of death and the actuarial present values of the whole life insurance and annuity. The heterogeneity or frailty effect of a cohort can be expressed explicitly. The model is also able to explain some stylized facts of observed mortality data. We fit the model to some Swedish population cohort data and life tables compiled by the U.S. Social Security Administration. The fitting results are very satisfactory.     

The Higher Earning in America: Are 529 Plans a Good Way to Save for College?

This article studies whether 529 plans are an effective way for most people to save for college. The 529 plans were created in 1996 to help low- and middle-income American families save for college. Since this time they have adopted more tax advantages and grown substantially as a result. While total balances in 529 plans now exceed $250 billion, less than 3.0 percent of households have a 529 plan. And the majority of 529 plan accounts are held by the wealthiest households. Low- and middle-income households receive little tax savings from investing in 529 plans, and some states count these plans against financial aid. Also, 529 plans are complicated, rules vary by state, and fund management fees tend to be high. Thus, 529 plans are not the panacea to college affordability.     

Multiperiod Optimal Investment-Consumption Strategies with Mortality Risk and Environment Uncertainty

Abstract

In this article we investigate three related investment-consumption problems for a risk-averse investor: (1) an investment-only problem that involves utility from only terminal wealth, (2) an investment-consumption problem that involves utility from only consumption, and (3) an extended investment-consumption problem that involves utility from both consumption and terminal wealth. Although these problems have been studied quite extensively in continuous-time frameworks, we focus on discrete time. Our contributions are (1) to model these investmentconsumption problems using a discrete model that incorporates the environment risk and mortality risk, in addition to the market risk that is typically considered, and (2) to derive explicit expressions of the optimal investment-consumption strategies to these modeled problems. Furthermore, economic implications of our results are presented. It is reassuring that many of our findings are consistent with the well-known results from the continuous-time models, even though our models have the additional features of modeling the environment uncertainty and the uncertain exit time.     

“The Time of Recovery and the Maximum Severity of Ruin in a Sparre Andersen Model,” Shuanming Li,October 2008

Abstract

In a first-party recovery scheme for automobile property damage, the first-party insurer compensates not-at-fault vehicular damage. In this scheme, adjusters may not have the incentive to assign liability when the driver is, in fact, at fault for the accident. This is due to adjusters not having to coordinate with a third-party adjuster, and, for insureds that carry collision coverage, the assignment of fault does not appreciably affect the compensation paid out. This in turn reduces the effectiveness of the experience-rating component of the insurance premium. Empirical evidence that supports the presence of incorrect fault assignment is provided. A stochastic model of experience rating analyzing the impact of incorrect fault assignment on driving record classes confirms that low-risk insureds pay more for insurance than if fault was correctly assigned.     

Firm characteristics and audit committees complying with ’best practice‘ membership guidelines

This study investigates demand and supply characteristics associated with firms that voluntarily established audit committees meeting ‘best practice’ membership guidelines. We focus on a set of best practice criteria rather than on the separate elements of the best practice criteria as in past studies. We conduct our tests using a sample of New Zealand listed companies that, relative to firms in other capital markets, are smaller and have more concentrated ownership. This setting differs from prior research because we expect the costs of voluntarily achieving best practice to be reasonably high. The results show that demand factors are not significantly related to the presence of an audit committee that conforms with best practice membership guidelines. However, supply factors (i.e. those firms with larger and more independent boards) are more likely to form audit committees that meet best practice. These results suggest that compliance costs will be greater for firms with smaller and less independent boards of directors if they are required to comply with best practice requirements.     

Matching using semiparametric propensity scores

This paper considers the application of semiparametric methods to estimate propensity scores or probabilities of program participation, which are central to certain program evaluation methods. To evaluate the practical benefits, we first conduct a Monte Carlo study. Second, we use data from the NSW experiment, CPS, and PSID. We compare treatment effect and evaluation bias estimates using propensity scores estimated from parametric logit, semiparametric single index, and semiparametric binary quantile regression models. Our results suggest that it is important to account for very general forms of heterogeneity in (semiparametric) estimation of the propensity score, particularly when the treatment effects vary in an unsystematic manner with the true propensity score.