中国居民医疗保险购买行为研究-基于商业健康保险的角度

本文通过健康保险市场供需双方行为分析,构建居民医疗保险购买行为模型,利用中国健康与营养调查数据(2000—2006),运用部分观测的二元Probit估计方法(Bivariate Probit with partial observability),从实证的角度分析商业健康保险市场中供需双方各自的风险选择行为,以及城乡地区居民对商业健康保险的潜在需求行为及其宏微观影响因素。本文发现:(1)城乡居民都存在显著的逆向选择行为;(2)城乡社会医疗保障对居民商业健康保险需求行为有显著的促进作用;(3)影响居民商业健康保险行为的其他因素还包括,个人的风险偏好和经济购买力。     

A Simple Exposition of the Social Security Trust Fund

Health insurance policy is a current topic of concern for the United States. The classroom game discussed here provides students with a thorough understanding of some of the policy options under debate, in addition to demonstrating the classic problem of adverse selection. Students received probabilities of encountering a variety of medical expenses, based on their randomly assigned fictitious person’s age and health status. In each round, students made insurance decisions and then rolled dice to determine outcomes for each possible medical expense. The experiment considered insurance with an individual mandate, insurance without an individual mandate, insurance where students could purchase à la carte coverage mimicking proposed insurance riders for certain coverage, and insurance where pre-existing conditions were not covered.     

Community rating and the market for private non-group health insurance

Prior research on adverse selection in health insurance markets has found only mixed evidence for adverse selection in group settings. We examine the impact of state community rating regulations enacted in the 1990s, which greatly limited insurers' ability to risk rate premiums, to determine if adverse selection is more evident in non-group insurance markets. Using data from large, national surveys we find evidence of a shift to a less healthy pool of non-group enrollees as a consequence of community rating. Community rating made healthy people 20 to 60% less likely to be insured by non-group health insurance; in addition, we found evidence that young and healthy people were 20 to 30% more likely to be uninsured as a result of community rating. We also find evidence that individuals in poor health were 35 to 50% more likely to be insured in the non-group market, but only limited evidence suggesting that persons in poor health were less likely to be uninsured. Our results are further supported by findings suggesting that non-group enrollees were sicker as a result of the community rating laws. Lastly, we find evidence suggesting that HMO penetration in the non-group market increased disproportionately in states that implemented community rating relative to states that did not.     

Minimum standards, insurance regulation and adverse selection: evidence from the Medigap market

This paper examines the implications of minimum standards for insurance markets. I study the imposition of binding minimum standards on the market for voluntary private health insurance for the elderly. The central estimates suggest that the introduction of the standards was associated with an 8 percentage point (25%) decrease in the proportion of the population with coverage in the affected market, with no evidence of substitution toward other, unregulated sources of insurance coverage. To explore possible factors contributing to the impact of the minimum standards, I develop comparative static predictions of the impact of imposing minimum standards in an insurance market with adverse selection. The observed changes in market equilibrium associated with the minimum standards are broadly consistent with these predictions, providing evidence of the existence of adverse selection in this insurance market. More importantly, they suggest that the presence of adverse selection—which in principle may provide an economic rationale for minimum standards—in practice may have exacerbated the declines in insurance coverage associated with the minimum standards.     

Taxation,insurance, and precautionary labor

We examine optimal taxation and social insurance with adverse selection in competitive insurance markets. In a previous literature, it has been shown that, with perfect insurance markets, social insurance improves welfare since it is able to redistribute without creating distortions. This result has been taken as robust to the introduction of adverse selection as this would only provide additional justifications for social insurance. We show, however, that adverse selection can weaken the case for social insurance compared to a situation with perfect markets. Whenever social insurance mitigates private underinsurance, it also causes welfare-reducing effects by decreasing precautionary labor supply and hence tax revenue. In addition, adverse selection may reduce the redistributive potential of social insurance. We illustrate our general results using different equilibrium concepts for the insurance market. Notably, we derive conditions under which a complete renunciation of social insurance is optimal and the government only relies on income taxation to achieve its redistributive objectives.     

The determinants of the demand for private health insurance under Medicare

Since the introduction of Medicare in 1984, the proportion of the Australian population with private health insurance has declined considerably. Insurance for health care consumption is compulsory for the public health sector but optional for the private health sector. In this paper, we explore a number of important issues in the demand for private health insurance in Australia. The socio-economic variables which influence demand are examined using a binary logit model. A number of simulations are performed to highlight the influence and relative importance of various characteristics such as age, income, health status and geographical location on demand. A number of important policy issues in the private health insurance market are highlighted. First, evidence is provided of adverse selection in the private health insurance pool, second, the notion of the wealthy uninsured is refuted, and finally it is confirmed that there are significant interstate differences in the demand for private health insurance.     

ESTIMATING WELFARE IN INSURANCE MARKETS USING VARIATION IN PRICES

We provide a graphical illustration of how standard consumer and producer theory can be used to quantify the welfare loss associated with inefficient pricing in insurance markets with selection. We then show how this welfare loss can be estimated empirically using identifying variation in the price of insurance. Such variation, together with quantity data, allows us to estimate the demand for insurance. The same variation, together with cost data, allows us to estimate how insurer's costs vary as market participants endogenously respond to price. The slope of this estimated cost curve provides a direct test for both the existence and nature of selection, and the combination of demand and cost curves can be used to estimate welfare. We illustrate our approach by applying it to data on employer-provided health insurance from one specific company. We detect adverse selection but estimate that the quantitative welfare implications associated with inefficient pricing in our particular application are small, in both absolute and relative terms.     

Dynamic adverse selection and the supply size

In this paper we examine the problem of dynamic adverse selection in a stylized market where the quality of goods is a seller׳s private information while the realized distribution of qualities is public information. We obtain that full trade occurs in every dynamic competitive equilibrium. Moreover, we show that if prices can be conditioned on the supply size then a dynamic competitive equilibrium always exists, while it fails to exist if prices cannot be conditioned on the supply size and the frequency of exchanges is high enough. We conclude that the possibility to condition prices on the supply size allows us to reach efficiency in the limit for exchanges becoming more and more frequent, while otherwise the welfare loss due to delays of exchanges remains bounded away from zero.     

Price signaling and the strategic benefits of price rigidities

We analyze trade between a perfectly informed price setting party (seller) and an imperfectly informed price taker (buyer). Differently from most of the literature, we focus on the case in which, under full information, it would be inefficient to trade goods of sufficiently poor quality. We show that the unique equilibrium surviving D1 is characterized by market breakdown, although trade would be mutually beneficial in some state of nature. This occurs independently of the precision of the information available to the buyer. The model thus implies that signaling through prices may exacerbate the effect of adverse selection rather than mitigate it. Under D1, the seller would always benefit from committing to prices that do not reveal her information. We develop this intuition by analyzing the strategic advantages of price rigidities. We show that price rigidities help restore trade and could even enhance effectiveness of prices as signals of quality.     

Information Asymmetries and Risk Management in Healthcare Markets: The U.S. Affordable Care Act in Retrospect

This article critically examines the pertinent issues in ex ante and ex post moral hazard in healthcare markets, with the U.S. Affordable Care Act (ACA) as its focal point of inquiry. First, it compares the various types of information asymmetries resulting from the production, allocation, and utilization of health insurance. Second, it reviews the literature on adverse selection, moral hazard, and risk mitigation against which salient ACA reforms are analyzed. In contrasting conventional moral hazard from an alternative theory of welfare maximization, it suggests that healthcare (over)utilization cannot necessarily be considered wasteful, even if it ends up costing insurers more on a short-term basis. Costs and savings attributable to healthcare spending under the ACA will vary between the consumer, insurer, and regulator-subsidizer. Despite the ambiguities surrounding definitions of “health,” the challenge of containing inefficient moral hazard, and encouraging its desirable counterpart, lies in the tradeoffs that arise between consumer access to affordable and quality healthcare and the market competitiveness of health insurers. The new Trump administration will have to address these tradeoffs in repealing and replacing the ACA, particularly in light of escalating insurance premiums and deductibles, narrower provider networks, and technical implementation issues.     

Information Revelation and Market Incompleteness

This paper introduces a theory of market incompleteness based on the information transmission role of prices and its adverse impact on the provision of insurance in financial markets. We analyse a simple security design model in which the number and payoff of securities are endogenous. Agents have rational expectations and differ in information, endowments, and attitudes toward risk. When markets are incomplete, equilibrium prices are typically partially revealing, while full relevation is attained with complete markets. The optimality of complete or incomplete markets depends on whether the adverse selection effect (the unwillingness of agents to trade risks when they are informationally disadvantaged) is stronger or weaker than the Hirshleifer effect (the impossibility of trading risks that have already been resolved), as new securities are issued and prices reveal more information. When the Hirshleifer effect dominates, an incomplete set of securities is preferred by all agents, and generates a higher volume of trade.     

Price Competition and Consumer Externalities in a Vertically Differentiated Duopoly with Information Disparities

In this paper, we extend the model of vertical product differentiation to consider information disparities about quality differences and their effects on price competition. If uninformed consumers overestimate vertical differentiation, asymmetric information is a source of market power and informed consumers exert positive externalities on high quality product purchasers and negative externalities on low quality product purchasers. Such a result is consistent with the fact that information undermines brand. If uninformed consumers are skeptical, adverse selection issues arise and market demands may be perfectly inelastic to prices. With elastic demands equilibrium prices may be either distorted downwards or reflect real quality if the share of informed consumers is suffciently high. Therefore, with skeptical consumers firms may want either to signal quality or subsidize information provision.     

Adverse selection and statistical discrimination: An analysis of Canadian automobile insurance

Statistical discrimination occurs when a characteristic, such as sex, is used as an indicator of the risk group of an individual. The theory of adverse selection is used to explain the occurrence of statistical discrimination. A model of the market for collision insurance, which is based on the theory of adverse selection, is estimated on Canadian data. The results suggest that adverse selection occurs in this market. Simulations of the effect of prohibiting sexual discrimination in the 21–24 age group indicate that the premiums for single females would increase substantially and that a significant proportion would no longer purchase collision insurance.     

Adverse selection in annuity markets: Evidence from the British Life Annuity Act of 1808

We study adverse selection using data from an 1808 Act of British Parliament that effectively opened a market for life annuities. Our analysis indicates significant selection effects. The evidence for adverse selection is strongest for a sub-sample of annuitants whose annuities were purchased by profit-seeking speculators, a sub-sample in which “advantageous selection” resulting from multi-dimensional heterogeneity is unlikely to have been significant. These results support the view that adverse selection can be masked by advantageous selection in empirical studies of standard insurance markets.     

MIDDLEMEN AND THE ADVERSE SELECTION PROBLEM

We demonstrate that the coexistence of an uncoordinated search market and a middleman market may alleviate adverse selection in the trade of goods of different quality. Inability to conduct trade penalizes sellers of low‐quality goods disproportionately, encouraging them to trade via middlemen. A semi‐separating equilibrium exists when a sufficient number of sellers of low‐quality goods choose the middleman market to allow high‐quality goods to be successfully traded in the search market. The result may explain why a search market can survive alongside a coordinated market, a phenomenon characteristic, for example, of markets for used cars, housing and labour.     

Does asymmetric information matter in the early insurance market? Evidence from the auto insurance market

In the late 1960s, the performance of automobile insurance declined dramatically in Japan in spite of rapid growth in the diffusion rate, and the premiums were sharply raised several times in order to improve the situation. This observation indicates the possible presence of adverse selection (death spiral), and provides an ideal situation for assessing informational asymmetry. Using bodily injury liability (BIL) insurance data from 46 Japanese prefectures over the period 1966 to 1975, this article tests two hypotheses of adverse selection: (i) high-risk drivers were more likely to join the BIL insurance market and (ii) sharp premium increases drove low-risk policyholders away. Various empirical analyses show that there is little evidence for either type of adverse selection. We also test whether a risk-misperception hypothesis can explain our results, and find some evidence that the population density have a significantly positive impact on the demand for BIL insurance.     

城镇基本医疗保险中逆向选择的检验

本文利用城镇居民基本医疗保险试点评估调查的数据,实证检验了我国城镇居民和职工基本医疗保险中的逆向选择问题。本文的实证结果证实了逆向选择的存在:在未被城镇职工基本医疗保险覆盖的城镇人群中,健康状况较差的个体更倾向于参加城镇居民基本医疗;城镇居民基本医疗保险的参保者接受门诊和住院服务利用率的概率更高;保险对住院服务利用率的影响大于对门诊的影响。另一方面,我们还发现在已被城镇职工基本医疗保险覆盖的人群中,健康状况较差的职工也更倾向于购买补充商业医保,但是健康状况最差的个体购买补充商业医保的概率最低,而购买商业医保后住院率显著增加。     

UNEMPLOYMENT POLICIES IN AN ECONOMY WITH ADVERSE SELECTION

This paper studies the effects of unemployment policies in a simple static general equilibrium model with adverse selection in the labour market. Firms offer a contract that induces the self‐selection of workers. In equilibrium, all unskilled workers are screened out and some skilled workers are rationed out. It is shown that the provision of unemployment insurance raises involuntary unemployment by encouraging adverse selection, while unemployment assistance – or subsidy to unemployment – reduces involuntary unemployment. A simple efficiency wage model is also presented to show that either of the two policies reduces employment by taxing effort and subsidizing shirking. The key is whether the social role of unemployment is a sorting device or a worker discipline device.     

A dynamic analysis of the demand for health insurance and health care

We find that asymmetric information is important for the uptake of supplementary private health insurance and health care utilization. We use dynamic panel data models to investigate the sources of asymmetric information and distinguish short-run selection effects into insurance from long-run selection effects. Short-run selection effects (i.e. responses to shocks) are adverse, but small in size. Also long-run effects driven by differences in, for example, preferences and risk aversion, are small. But we find some evidence for multidimensional asymmetric information. For example, mental health causes advantageous selection. Estimates of health care utilization models suggest that moral hazard is not important.     

Choice, price competition and complexity in markets for health insurance

The United States and other nations rely on consumer choice and price competition between competing health plans to allocate resources in the health sector. While a great deal of research has examined the efficiency consequences of adverse selection in health insurance markets, less attention has been devoted to other aspects of consumer choice. The nation of Switzerland offers a unique opportunity to study price competition in health insurance markets. Switzerland regulates health insurance markets with the aim of minimizing adverse selection and encouraging strong price competition. We examine consumer responses to price differences in local markets and the degree of price variation in local markets. Using both survey data and observations on local markets we obtain evidence suggesting that as the number of choices offered to individuals grows, their willingness to switch plans given a set of price dispersion differences declines, which allows large price differences for relatively homogeneous products to persist. We consider explanations for this phenomenon from economics and psychology.