Rational inattention,long-run consumption risk,and portfolio choice

This paper explores how the introduction of rational inattention (RI) – that agents process information subject to finite channel capacity – affects optimal consumption and investment decisions in an otherwise standard intertemporal model of portfolio choice. We first explicitly derive optimal consumption and portfolio rules under RI and then show that introducing RI reduces the optimal share of savings invested in the risky asset because inattentive investors face greater long-run consumption risk. We also show that the investment horizon matters for portfolio allocation in the presence of RI, even if investment opportunities are constant and the utility function of investors is constant relative risk aversion. Second, after aggregating across investors, we show that introducing RI can better explain the observed joint dynamics of aggregate consumption and the equity return. Finally, we show that RI increases the implied equity premium because investors under RI face greater long-run consumption risk and thus require higher compensation in equilibrium.     

GROWTH AND BUBBLES WITH CONSUMPTION EXTERNALITIES*

This paper explores the role of consumption externalities in an overlapping generations economy with capital accumulation. If consumers in each generation are concerned with other agents’ consumption behaviours, there exist intergenerational as well as intragenerational consumption externalities. It is the presence of intergenreational consumption externalities that may produce fundamental effects both on equilibrium dynamics and on steady‐state characterization of the economy. This paper demonstrates this fact in the context of a simple model of endogenously growing, overlapping‐generations economy with or without asset bubbles.     

CONSUMPTION AND LEISURE EXTERNALITIES, ECONOMIC GROWTH AND EQUILIBRIUM EFFICIENCY

This paper analyzes the effects of consumption and leisure externalities on growth and welfare in a two‐sector endogenous growth model with human capital accumulation. Both types of externalities are shown to affect the long‐run equilibrium and optimal growth rates in a rather different way. The relationship between the steady state of the market and the centrally planned economy is also analyzed. The optimal growth path can be decentralized by resorting to consumption or labor income taxation, whereas capital income should be untaxed. Numerical simulations suggest that growth and welfare effects of mild consumption and leisure externalities may be quantitatively important.     

Consumption externalities: a representative consumer model when agents are heterogeneous

We examine a growth model with consumption externalities where agents differ in their initial capital endowment and their reference group. We show under which conditions the aggregate equilibrium with heterogeneous agents replicates that obtained with a representative consumer, despite the fact that different individuals have different consumption levels. Next we consider the implications of the presence of consumption externalities for the long-run distributions of income and wealth. We find that, in a growing economy, “keeping up with the Joneses” results in less inequality than would prevail in an economy with no consumption externalities.     

Endogenous Home Bias in Portfolio Diversification and Firms’ Entry

The home bias in portfolios is considered a main puzzle in international macroeconomics. This paper provides a new benchmark for its analysis in a tractable new open economy macroeconomic model, where the home‐biased position is an optimal allocation. An equilibrium model of perfect risk‐sharing is specified, with endogenous portfolios and firm entry. Unlike in previous work, the international portfolio diversification is driven by home bias in capital goods—independently of home bias in consumption when countries are of equal size. The model explains the recent patterns of portfolio allocations in developed economies. Most important, optimal portfolio shares are independent of market dynamics.     

Consumption externality, efficiency and optimal taxation in one-sector growth model

In an economy with consumption externalities, existing studies find that a competitive equilibrium is efficient in the long run and remains efficient in transitions if preferences are homothetic. This paper revisits the efficiency issue in an otherwise standard one-sector growth model where consumption externalities affect a utility via their effects on the time preference. We find that even if preferences are homothetic, the externality changes the marginal rate of substitution between now and future and leads to a disparity in the intertemporal elasticity of substitution between the centrally planned economy and a decentralized economy. As a result, a competitive equilibrium is inefficient in transition dynamics. We characterize an optimal tax/subsidy structure that enables the allocation in a decentralized economy to replicate the social optimum.     

Private ownership economies with externalities and existence of competitive equilibria: a differentiable approach

We consider a general equilibrium model of a private ownership economy with consumption and production externalities. Utility functions and production technologies may be affected by the consumption and production activities of all other agents in the economy. We use homotopy techniques to show that the set of competitive equilibria is non-empty and compact. Fixing the externalities, the assumptions on utility functions and production technologies are standard in a differentiable framework. Competitive equilibria are written in terms of first order conditions associated with agents’ behavior and market clearing conditions, following the seminal paper of Smale (J Math Econ 1:1–14, 1974). The work of adapting the homotopy approach to economies with externalities on the production side is non-trivial and it requires some ingenious adjustments, because the production technologies are not required to be convex with respect to the consumption and production activities of all agents.     

ON THE ROLE OF THE GROWTH OPTIMAL PORTFOLIO IN FINANCE

The paper discusses various roles that the growth optimal portfolio (GOP) plays in finance. For the case of a continuous market we show how the GOP can be interpreted as a fundamental building block in financial market modeling, portfolio optimisation, contingent claim pricing and risk measurement. On the basis of a portfolio selection theorem, optimal portfolios are derived. These allocate funds into the GOP and the savings account. A risk aversion coefficient is introduced, controlling the amount invested in the savings account, which allows to characterize portfolio strategies that maximise expected utilities. Natural conditions are formulated under which the GOP appears as the market portfolio. A derivation of the intertemporal capital asset pricing model is given without relying on Markovianity, equilibrium arguments or utility functions. Fair contingent claim pricing, with the GOP as numeraire portfolio, is shown to generalise risk neutral and actuarial pricing. Finally, the GOP is described in various ways as the best performing portfolio.     

The Optimal Provision of Curative Goods

We analyze the optimal contract between a risk neutral regulator providing a curative goods and a risk averse patient who learns the realized value of his/her health status after the contracting stage. Consumption of a curative good (healthcare) reduces the disutility associated with a disease. We show that the consumption of curative goods is larger than in the complete information case, that this overprovision increases with the degree of patients’ risk‐aversion and the marginal cost of treatment. Ceilings on the amount of healthcare are part of the optimal contract when risk aversion is important.     

Optimal portfolio choices using financial leverage

This paper investigates the role of leverage in determining the investor's optimal asset allocation over multiperiod investment horizons. To do this, we allow investors to lever their financial position by borrowing from credit markets. GMM methods are used to estimate and test the optimal portfolio weights and individual's optimal choice of financial leverage. These optimal choices are assumed to be parametric functions of a set of state variables describing the evolution of the economy. The empirical application of this methodology to a portfolio of cash, bonds and stocks reveals that a) financial leverage limits the reaction of investors to changes in the investment opportunity set; b) individuals increase leverage during recessions and deleverage in expansionary periods; c) optimal portfolio weights and financial leverage are negatively related to the degree of investor's risk aversion and positively related to the investment horizon.     

Social Security and Old Age Unemployment Risk with Efficient Wage Bargaining

I analyze a life‐cycle economy with old age productivity risk where wages, employment, and severance payments are set through efficient bargaining between risk averse unions and risk neutral firms. Allocations with limited union membership are second‐best inefficient as they generate too little labor supply in young age, too much consumption before retirement, too little employment of older workers (early retirement), and too little insurance against old age unemployment. Providing public transfers to early retirees (disability benefits or early pensions) might help to increase the degree of risk sharing at the cost of lower old age employment. Depending on whether absolute risk aversion is increasing or decreasing in consumption, these policies might or might not produce efficiency gains at equilibrium.     

Imports, Status Preference, and Foreign Borrowing

This paper considers the implications of consumption and borrowing externalities in a small open economy framework. The former reflect the assumption that status conscious agents care about the relative consumption of imported goods, while the latter arise because agents do not take into account the effects of their borrowing decisions on the interest rate on debt. We analyze in the paper the impact of an increase in the degree of status preference on the saddlepath adjustment of the decentralized economy. In addition, the contrasting steady‐state and dynamic properties of the social planner’s economy are derived, along with the corresponding optimal tax and subsidy policies.     

Some Aggregate Effects of Heterogeneity in Information Processing

This paper analyzes the equilibrium of an economy where economic agents differ with respect to their information gathering and processing abilities. Our results depend on the magnitude of the relative risk aversion. We show that the unsophisticated (with respect to their information processing abilities) agents are disproportionately important in the cases of both large and small risk aversion. In the case of the relative risk aversion measure being greater than unity volatility of aggregate consumption is reduced. This supports the view that observed consumption in many countries fluctuates less than predicted by models with fully rational agents only.     

Trade,environment, and income inequality: An optimal taxation approach

In a small open economy, how should a government pursuing both environmental and redistributive objectives design domestic taxes when redistribution is costly? And how does trade liberalization affect the economy's levels of pollution and inequalities, when taxes are optimally and endogenously adjusted? Using a general equilibrium model under asymmetric information with two goods, two factors (skilled and unskilled labor), and pollution, this paper characterizes the optimal mixed tax system (nonlinear income tax and linear commodity and production taxes/subsidies) with both production and consumption externalities. While optimal income taxes are not directly affected by environmental externalities, conditions are derived under which under‐ or over‐internalization of social marginal damage is optimal for redistributive considerations. Assuming that redistribution operates in favor of the unskilled workers and that the dirty sector is intensive in unskilled labor, simulations suggest that trade liberalization involves a clear trade‐off between the reduction of inequalities and the control of pollution when the source of externality is only production; this is not necessarily true with a consumption externality. Finally, an increase in the willingness to redistribute income toward the unskilled results paradoxically in less pollution and more income inequalities.     

Estate taxes, consumption externalities, and altruism

We study how the introduction of consumption externalities affects the optimality of the dynamic equilibrium in an economy displaying dynastic altruism. When the bequest motive is inoperative consumption externalities affect the intertemporal margin between young and old consumption and thus modify the intertemporal path of aggregate consumption and capital. The optimal tax policy that solves this intertemporal suboptimality consists of a tax on capital income and a pay-as-you-go social security system. The latter solves the excess of capital accumulation due to the inoperativeness of the bequest motive and the former solves the suboptimal allocation of consumption due to consumption externalities. When the bequest motive is operative consumption externalities only cause an intratemporal misallocation of consumption but do not affect the optimality of the capital stock level. This suboptimal allocation of consumption implies in turn that the path of bequest deviates also from optimality. The optimal tax policy in this case consists of an estate tax and a capital income tax.     

WELFARE IMPLICATIONS OF THE INTERACTION BETWEEN HABITS AND CONSUMPTION EXTERNALITIES*

We analyze the welfare properties of the equilibrium path of a growth model where both habits and consumption externalities affect the utility of consumers. Our analysis highlights the crucial role played by complementarities between externalities and habits in order to generate an inefficient dynamic equilibrium. In particular, we show that the competitive equilibrium is inefficient when consumption externalities and habit‐adjusted consumption are not perfect substitutes.     

Asset pricing in a production economy with Chew–Dekel preferences

In this paper we provide a thorough characterization of the asset returns implied by a simple general equilibrium production economy with Chew–Dekel risk preferences and convex capital adjustment costs. When households display levels of disappointment aversion consistent with the experimental evidence, a version of the model parameterized to match the volatility of output and consumption growth generates unconditional expected asset returns and price of risk in line with the historical data. For the model with Epstein–Zin preferences to generate similar statistics, the relative risk aversion coefficient needs to be about 55, two orders of magnitude higher than the available estimates. We argue that this is not surprising, given the limited risk imposed on agents by a reasonably calibrated stochastic growth model.     

Sustained positive consumption in a model of stochastic growth: The role of risk aversion

In a stochastic economy, long run consumption and output may not be bounded away from zero even when productivity is arbitrarily high near zero and uncertainty is arbitrarily small. In the one-sector stochastic optimal growth model with i.i.d. production shocks, we characterize the nature of preferences that lead to this phenomenon for a stochastic Cobb–Douglas technology. For the general version of the model, we outline sufficient conditions under which the economy expands its capital stock near zero and long run consumption is bounded away from zero with certainty. Our conditions highlight the important role played by risk aversion for small consumption levels.     

考虑基准资产的动态投资组合选取

职业基金经理的目标经常是希望自己的投资组合以稳定的表现能够超越所某一基准资产或组合。因此本文给出一个考虑基准资产的动态均值——方差投资组合选取模型。假设状态之间的转移遵循马氏过程,给定状态转移矩阵,可以得到对风险资产最优投入的解析表达式。此表达式表明对风险资产的投入由三项构成,前两项是不考虑基准资产时对风险资产的投入,最后一项与基准资产有关;在基准资产上的权重由基准资产收益的大小来决定,与积极投资组合管理者的风险厌恶程度无关;随着风险厌恶程度的增加,管理者会减少在风险资产上的投入。数值分析显示考虑基准资产的投资组合是一个积极的投资组合。     

Optimal investment and consumption with return predictability and execution costs

We provide a closed-form solution to an optimal investment and consumption problem for a constant absolute risk aversion (CARA) agent, who faces execution costs when trading correlated risky assets with return predictability. The optimal investment strategy indicates that the agent should trade gradually toward a dynamic aim portfolio, which is an adjusted Merton portfolio with modifications to account for the persistence of the return-predicting signals and the execution costs. The optimal consumption strategy is quadratic in the return-predicting signals and linear in the agent's wealth. Our numerical studies show that the execution costs diminish the importance of asset return predictability on the agent's optimal investment strategy, thereby confirming the conjecture raised by Liu (2004). In addition, the presence of the intermediate consumption leads to a more aggressive aim portfolio than the case without consumption.