Strategy-proof risk sharing

We consider risk sharing problems with a single good and a finite number of states. Agents have a common prior and their preferences are represented in the expected utility form and are risk averse. We study efficient and individually rational risk sharing rules satisfying strategy-proofness, the requirement that no one can ever benefit by misrepresenting his preference. When aggregate certainty holds, we show that “fixed price selections” from Walrasian correspondence are the only rules satisfying efficiency, individual rationality, and strategy-proofness. However, when aggregate uncertainty holds, we show that there exists no rule satisfying the three requirements. Moreover, in the two agents case, we show that dictatorial rules are the only efficient and strategy-proof rules. Dropping the common prior assumption in the model, we show that this assumption is necessary and sufficient for the existence of rules satisfying the three main requirements in the two agents and aggregate certainty case.     

Social security and risk sharing

In this paper we identify conditions under which the introduction of a pay-as-you-go social security system is ex ante Pareto-improving in a stochastic OLG economy with capital accumulation and land. We argue that these conditions are consistent with realistic specifications of the parameters of the economy. In our model financial markets are complete and competitive equilibria interim Pareto efficient. Therefore, a welfare improvement can only be obtained if agents? welfare is evaluated ex ante, and arises from an improvement in intergenerational risk sharing. We also examine the optimal size of a given social security system as well as its optimal reform.     

Optimal risk sharing with background risk

This paper examines qualitative properties of efficient insurance contracts in the presence of background risk. In order to get results for all strictly risk-averse expected utility maximizers, the concept of “stochastic increasingness” is used. Different assumptions on the stochastic dependence between the insurable and uninsurable risk lead to different qualitative properties of the efficient contracts. The new results obtained under hypotheses of dependent risks are compared to classical results in the absence of background risk or to the case of independent risks. The theory is further generalized to nonexpected utility maximizers.     

贸易自由化与中国贸易结构升级

贸易自由化是加深经济全球化程度的主要因素,我国在逐步融入经济全球化的进程中,贸易自由化将会对我国外贸结构产生重大影响.本文根据贸易自由化对贸易结构变动效应的分析,用以各自科学的衡量指标,着重从理论和实证两个方面研究分析两者间的影响作用,进而提出相应的政策建议.     

Political intergenerational risk sharing

In a stochastic two-period OLG model, featuring an aggregate shock to the economy, ex-ante optimality requires intergenerational risk sharing. We compare the level of intergenerational risk sharing chosen by a benevolent government and by an office-seeking politician. In our political system, the transfer of resources across generations is determined as a Markov equilibrium of a probabilistic voting game. Low realized returns on the risky asset induce politicians to compensate the old through a PAYG system. This political system typically generates an intergenerational risk sharing scheme that is (i) larger, (ii) more persistent, and (iii) less responsive to the realization of the shock than the social optimum. This is because the current politician anticipates her transfers to the elderly to be compensated by future politicians through offsetting transfers, and hence overspends.     

International risk sharing and commodity prices

Abstract Cole and Obstfeld (1991) exposited a classic result where equilibrium movements in the terms of trade could make ex ante risk‐sharing arrangements unnecessary: a unity elasticity of substitution across goods and production specialization. This paper extends their model to N countries and M commodities (N > M). Here the terms of trade provides insurance against commodity‐specific shocks, not country‐specific shocks. Using commodity‐level production data at the national level and world commodity prices, we document significant terms of trade variability and positive responses of nation‐specific production to terms of trade improvements. The endogenous terms of trade insurance mechanism highlighted in CO is virtually non‐existent.     

Trade integration and synchronization of shocks*

According to the European Commission (1990 ), closer integration leads to less frequent asymmetric shocks and to more synchronized business cycles between countries. However, for Krugman (1993 ) closer integration implies higher specialization and, thus, higher risks of idiosyncratic shocks. Drawing on the evidence from a group of transition countries, this paper tries to determine whose argument is supported by the data. This is done by confronting estimated time‐varying coefficients of supply and demand shock asymmetry with indicators of trade intensity and exchange rates. We find that (i) an increase in trade intensity leads to higher symmetry of demand shocks: the effect of integration on supply shock asymmetry varies from country to country; and (ii) a decrease in exchange rate volatility has a positive effect on demand shock convergence. The results confirm ‘The European Commission view’ and also the argument by Kenen (2001 ) according to which the impact of trade integration on shock asymmetry depends on the type of shock.     

Public versus private risk sharing

Can public income insurance through progressive income taxation improve the allocation of risk in an economy where private risk sharing is incomplete? The answer depends crucially on the fundamental friction that limits private risk sharing in the first place. If risk sharing is limited because insurance markets are missing for model-exogenous reasons (as in Bewley (1986) [8]) publicly provided risk sharing improves on the allocation of risk. If instead private insurance markets exist but their use is limited by limited enforcement (as in Kehoe and Levine (1993) [23]) then the provision of public insurance interacts with equilibrium private insurance, as, by providing risk sharing, the government affects the value of exclusion from private insurance markets and thus the enforcement mechanism of these contracts. We characterize consumption allocations in an economy with limited enforcement and a continuum of agents facing plausible income risk and tax systems with various degrees of progressivity (public risk sharing). We provide conditions under which more publicly provided insurance actually reduces total insurance for agents (excess crowding-out), or under which more public insurance increases total insurance (partial crowding-out).     

Trade integration and the EU economic membership criteria

The purpose of this paper is to consider whether the European Union (EU)'s economic membership criteria for the Central and Eastern European countries (CEECs) and Cyprus (the Candidate Countries) are fulfilled. To this end, I examine the actual and potential levels of trade between the Candidate Countries and the EU countries using the gravity model. The results show a high degree of trade integration between all Candidate Countries and the EU, indicating that the Candidate Countries would not face any serious difficulties in coping with the competitive pressure and market forces within the Union in the medium term. The European Commission, however, suggested the contrary for some of the Candidate Countries in its opinions of 1997.     

The formation of risk sharing networks

This paper examines the formation of risk sharing networks in the rural Philippines. We find that geographic proximity–possibly correlated with kinship–is a major determinant of mutual insurance links among villagers. Age and wealth differences also play an important role. In contrast, income correlation and differences in occupation are not determinants of network links. Reported network links have a strong effect on subsequent gifts and loans. Gifts between network partners are found to respond to shocks and to differences in health status. From this we conclude that intra-village mutual insurance links are largely determined by social and geographical proximity and are only weakly the result of purposeful diversification of income risk. The paper also makes a methodological contribution to the estimation of dyadic models.     

On optimality in intergenerational risk sharing

Summary. This paper defines and studies optimality in a dynamic stochastic economy with finitely lived agents, and investigates the optimality properties of an equilibrium with or without sequentially complete markets. Various Pareto optimality concepts are considered, including interim and ex ante optimality. We show that, at an equilibrium with a productive asset (land) and sequentially complete markets, the intervention of a government may be justified, but only to improve risk sharing between generations. If markets are incomplete, constrained interim optimality is investigated in two-period lived OLG economies. We extend the optimality properties of an equilibrium with land and give conditions under which introducing a pay-as-you-go system at an equilibrium would not lead to any Pareto improvement. Received: October 5, 1998; revised version: April 3, 2001     

Intergenerational redistribution and risk sharing with changing longevity

Trend increases in longevity are a global phenomenon challenging the fiscal sustainability of current welfare arrangements. Policy proposals abound and often build on implicit assertions concerning intergenerational equity. This paper offers a simple but manageable OLG model with endogenous retirement and cohort-specific longevity to address intergenerational redistribution and risk sharing. While it is well known that a utilitarian planner strives for consumption smoothing, it is shown that healthy ageing calls for work smoothing in the sense that retirement ages increase with longevity. Hence, cohorts with higher longevity should contribute to their larger consumption needs via later retirement, although it is shown that the planner still front-loads some financing (pre-saving). Stochastic longevity raises the issue of intergenerational risk sharing, which implies that cohorts turning out to have a high longevity are compensated at the expense of cohorts turning out to have a relatively short longevity.     

Regional consumption dynamics and risk sharing in Italy

In this paper, we propose a new method for investigating consumption insurance. Differently from the existing literature, we use error correcting VAR models in order to capture simultaneously the occurrence of risk sharing against permanent and transitory shocks. The proposed method is applied to the case of Italian regions. Empirical results obtained over the 1960–2001 period reveal that contrary to previous findings, Italian regions seem to shield against permanent shocks other than transitory ones. Although some biases are detected in the allocation process of resources, deviations from full consumption insurance are not as relevant as claimed in the previous literature on the Italian regions.     

Aggregate fluctuations, financial constraints and risk sharing

Summary. Private information and costly state verification often result in credit rationing in models with smooth investment, affecting both loan size and total investment. The optimal contract is derived in a dynamic stochastic growth model with capital for two types of models: one with symmetric information and the other with asymmetric information and costly state verification. When all information is observed costlessly, the equilibrium optimal contract provides complete insurance to risk-averse savers against aggregate fluctuations. When information is asymmetric and there is costly state verification, the equilibrium optimal contract provides only partial insurance against aggregate shocks. The extent of insurance is measured by the marginal rate of transformation of consumption between borrowers and lenders which is closely linked to the user cost of capital. The deadweight monitoring costs create a wedge between a borrower's cost of capital and a lender's stochastic discount factor, with two results: (i) fluctuations in the user cost of capital provides a mechanism by which aggregate shocks can be␣propagated; (ii) the distribution of capital's share of output among borrowers, lenders, and monitoring costs varies even if capital's share is constant. Capital market frictions not only amplify aggregate fluctuations but also generate cross-sectional fluctuations that may not be observable in aggregate data. Received: November 17, 1997; revised version: April 20, 1998     

Collateral premia and risk sharing under limited commitment

A competitive general equilibrium model with complete collateralized contracts under limited commitment is proposed and analyzed. With limited aggregate collateral, risk sharing is imperfect. There exists a minimal spanning set of finite collateralized contracts that generates the feasible space and that contains more than the complete set of collateralized Arrow securities. Examples show that exogenously restricting feasible contracts has a significant impact on agents’ welfare. I prove that constrained optimal allocations can be decentralized as a general equilibrium with collateral constraints, and vice versa. Because a capital good serves as collateral, it has an additional value, called collateral premium. The collateral premium is zero if and only if risk sharing is perfect. This is a testable implication of the model.     

Portfolio allocation and international risk sharing

Abstract We show that recent explanations of the consumption‐real exchange rate anomaly that rely on goods and financial market frictions are not robust to introducing just one additional international asset. When portfolios are selected optimally, international trade in two nominal bonds implies a consumption‐real exchange rate correlation that is too high compared with the data even when there are many shocks. Monetary policy specification plays a potentially important role for the degree of risk sharing provided by nominal bonds, both in the benchmark model with only tradable and non‐tradable sector supply shocks and also in the model that allows for news.     

International risk sharing during the globalization era

Abstract. Though financial globalization should improve international risk sharing, empirical support is lacking. We develop a simple welfare‐based measure that captures how far countries are from the ideal of perfect risk sharing. Applying it to data, we find some evidence that international risk sharing has improved during globalization. Improved risk sharing comes mostly from the convergence in rates of consumption growth among countries rather than from synchronization of consumption at the business cycle frequency.     

Segmented risk sharing in a continuous-time setting

Summary. The economy we study is comprised of a continuum of individuals. Each has a stochastic endowment that evolves continuously and independently of all other individuals' endowment processes. Individuals are risk averse and would therefore like to insure their endowment processes. The mutual independence of their endowment processes makes it feasible for them to obtain this insurance by pooling their endowments. We investigate whether such a scheme would survive as an equilibrium in a noncooperative setting. Received: October 16, 2000; revised version: August 8, 2001     

Incomplete risk sharing arrangements and the value of information

Summary. The paper constructs a theoretical framework in which the value of information in general equilibrium is determined by the interaction of two opposing mechanisms: first, more information about future random events leads to better individual decisions and, therefore, higher welfare. This is the ‘Blackwell effect’ where information has positive value. Second, more information in advance of trading limits the risk sharing opportunities in the economy and, therefore, reduces welfare. This is the ‘Hirshleifer effect’ where information has negative value. We demonstrate that in an economy with production information has positive value if the information refers to non-tradable risks; hence, such information does not destroy the Blackwell theorem. Information which refers to tradable risks may invalidate the Blackwell theorem if the consumers are highly risk averse. The critical level of relative risk aversion beyond which the value of information becomes negative is less than 0.5. Received: May 14, 2001; revised version: March 5, 2002