Economics - Research Publications

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    Semicoherent Multipopulation Mortality Modeling: The Impact on Longevity Risk Securitization
    Li, JS-H ; Chan, W-S ; Zhou, R (Wiley, 2017-09)
    Multipopulation mortality models play an important role in longevity risk transfers involving more than one population. Most of the existing multi‐population mortality models are built on the hypothesis of coherence, which assumes that there always exists a force that brings the mortality differential between any two populations back to a constant long‐term equilibrium level. This hypothesis prevents diverging long‐term forecasts, which do not seem to be biologically reasonable. However, the coherence assumption may be perceived by market participants as too strong and is in fact not always supported by empirical observations. In this article, we introduce a new concept called “semicoherence,” which is less stringent in the sense that it permits the mortality trajectories of two related populations to diverge, as long as the divergence does not exceed a specific tolerance corridor, beyond which mean reversion will come into effect. We further propose to produce semicoherent mortality forecasts by using a vector threshold autoregression. The proposed modeling approach is illustrated with mortality data from U.S. and English and Welsh male populations, and is applied to several pricing and hedging scenarios.
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    The Boundary of the Market for Biosecurity Risk
    Stoneham, G ; Hester, SM ; Li, JS-H ; Zhou, R ; Chaudhry, A (WILEY, 2021-08)
    Imported goods create value in destination countries but also create biosecurity risk. Although widely used in other domains of the economy, risk markets have not been created to manage losses that occur when exotic pests and diseases are introduced with traded goods. In this article we show that not all biosecurity risks are insurable. Losses arising from effort needed to detect and respond to exotic pests and diseases that breach national borders appear to be insurable because entry of these threats and consequent response costs, can be regarded as random events. As pests and diseases establish and spread, however, loss of access to export markets and productivity losses display systematic risk and appear to be uninsurable. Other insurability criteria support this definition of the boundary of biosecurity risk markets. We use the Australian biosecurity system as an example, although the framework described in this study will be applicable to biosecurity systems worldwide. We argue that biosecurity risk insurance could be incorporated into the current biosecurity system but would require legislation mandating importers to purchase insurance. Advantages of actuarial pricing of biosecurity risk are: (i) an increase in economic efficiency to the extent that importers respond to the price of biosecurity risk; (ii) financial sustainability would improve because actuarial pricing creates a structural link between funds available for biosecurity activities and risk exposure; and (iii) equity issues evident in the current biosecurity system could be addressed because risk creators (importers) would fund response activities through the purchase of insurance.
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    A General Semi-Markov Model for Coupled Lifetimes
    Ji, M ; Zhou, R (Taylor & Francis (Routledge), 2019-02-15)
    Joint-life annuities with a high last survivor benefit play an important role in the optimal annuity portfolio for a retired couple. The dependence between coupled lifetimes is crucial for valuing joint-life annuities. Existing bivariate modeling of coupled lifetimes is based on outdated data with limited observation periods and does not take into account mortality improvement. In this article, we propose a transparent and dynamic framework for modeling coupled lifetime dependence caused by both marital status and common mortality improvement factors. Dependence due to marital status is captured by a semi-Markov joint life model. Dependence due to common mortality improvement, which represents the correlation between mortality improvement patterns of coupled lives, is incorporated by a two-population mortality improvement model. The proposed model is applied to pricing the longevity risk in last survivor annuities sold in the United States and the United Kingdom.