STATIC FUND SEPARATION OF LONG‐TERM INVESTMENTS

This paper proves a class of static fund separation theorems, valid for investors with a long horizon and constant relative risk aversion, and with stochastic investment opportunities. An optimal portfolio decomposes as a constant mix of a few preference‐free funds, which are common to all investors. The weight in each fund is a constant that may depend on an investor's risk aversion, but not on the state variable, which changes over time. Vice versa, the composition of each fund may depend on the state, but not on the risk aversion, since a fund appears in the portfolios of different investors. We prove these results for two classes of models with a single state variable, and several assets with constant correlations with the state. In the linear class, the state is an Ornstein–Uhlenbeck process, risk premia are affine in the state, while volatilities and the interest rate are constant. In the square root class, the state follows a square root diffusion, expected returns and the interest rate are affine in the state, while volatilities are linear in the square root of the state.     

ENDOGENOUS JOB CONTACT NETWORKS

We develop a model where workers, anticipating the risk of becoming unemployed, invest in connections in order to access information about available jobs that other workers may have. The investment in connections is high when the job separation rate in the labor market is moderate, whereas it is low for either low or high levels of job separation rate. The equilibrium response of network investment to changes in the labor market conditions generates novel empirical predictions. In particular, the probability that a worker finds a new job via his connections increases in the separation rate when the separation rate is low, whereas it decreases when the separation rate is high. These predictions are supported by the empirical patterns that we document for the U.K. labor market.     

DYNAMIC TRADING VOLUME

We derive the process followed by trading volume, in a market with finite depth and constant investment opportunities, where a large investor, with a long horizon and constant relative risk aversion, trades a safe and a risky asset. Trading volume approximately follows a Gaussian, mean‐reverting diffusion, and increases with depth, volatility, and risk aversion. Unlike the frictionless theory, finite depth excludes leverage and short sales because such positions may not be solvent even with continuous trading.     

Targeting welfare in Italy: old problems and perspectives on reform

This paper has two principal objectives. Using a tax‐benefit microsimulation model and the 1998 micro data of the Bank of Italy survey of household income and wealth, we first study the distributional effects of the current Italian income maintenance system and highlight its main defects and limitations, concerning in particular its unequal coverage of the population and its low efficiency in fighting poverty. The second aim is to describe and analyse the reforms recently implemented in this field; in particular, the Italian government has reformed the targeting criteria and introduced three new cash transfers. We describe these reforms both in their institutional characteristics and in their likely distributional consequences, and examine whether and to what extent they are able to overcome the shortcomings of the current system.     

Choquet Rationality

Consider a decision problem under uncertainty for a decision maker with known (utility) payoffs over prizes. We say that an act is Choquet (Shafer, Bernoulli) rational if for some capacity (belief function, probability) over the set of states, it maximizes her “expected” utility. We show that an act may be Choquet rational without being Bernoulli rational, but it is Choquet rational if and only if it is Shafer rational. Journal of Economic Literature Classification Numbers: C72, D81.     

Multiple versus Single Banking Relationships: Theory and Evidence

A theory of the optimal number of banking relationships is developed and tested using matched bank-firm data. According to the theory, relationship banks may be unable to continue funding profitable projects owing to internal problems and a firm may thus have to refinance from nonrelationship banks. The latter, however, face an adverse selection problem, as they do not know the quality of the project, and may refuse to lend. In these circumstances, multiple banking can reduce the probability of an early liquidation of the project. The empirical evidence supports the predictions of the model.     

Summary of Findings of the Guido Carli Association's Second International Conference

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