4,098 research outputs found

    Constructive Fractional-Moment Criteria for Localization in Random Operators

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    We present a family of finite-volume criteria which cover the regime of exponential decay for the fractional moments of Green functions of operators with random potentials. Such decay is a technically convenient characterization of localization for it is known to imply spectral localization, absence of level repulsion, dynamical localization and a related condition which plays a significant role in the quantization of the Hall conductance in two-dimensional Fermi gases. The constructive criteria also preclude fast power-law decay of the Green functions at mobility edges.Comment: Announcement and summary of results whose proofs are given elsewhere. LaTex (10 pages), uses Elsevier "elsart" files (attached

    Lebowitz Inequalities for Ashkin-Teller Systems

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    We consider the Ashkin-Teller model with negative four-spin coupling but still in the region where the ground state is ferromagnetic. We establish the standard Lebowitz inequality as well as the extension that is necessary to prove a divergent susceptibility.Comment: Ams-TeX, 12 pages; two references added, final version accepted for publication in Physica

    Optimal Wage Re-Negotiation

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    This paper investigates an economy in which there are short-term wage contracts that are re-negotiated under certain conditions. This paper determines the optimal frequency of wage re-negotiation and shows that it depends positively on measures of aggregate variability and Phillips curve slope. The role of optimal wage re-negotiation is to mitigate the output effects of various shocks. In the context of an open economy, it is shown that the desirable exchange rate regime in an economy with optimal wage re-negotiation depends on the stochastic structure of the economy.

    Optimal Buffer Stocks and Precautionary Savings with Disappointment Aversion

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    Developing countries use various risk reduction schemes, ranging from active management of buffer stocks and international reserves to commodity stabilization funds. The purpose of this paper is to reexamine the design of these schemes in a generalized expected utility maximization model where agents are disappointment averse. We derive first the generalized risk premium, showing that disappointment aversion increases the conventional risk premium by a term proportional to the standard deviation times the degree of disappointment aversion. Next, we show that disappointment aversion modifies the characteristics of precautionary saving. The concavity of the marginal utility continues to determine precautionary saving, but its effect is of a second order magnitude (proportional to the variance) compared to the first order effect (proportional to the standard deviation) induced by disappointment aversion. Hence, higher volatility increases the precautionary saving of a disappointment averse agent. This result applies even if the income process approaches a random walk. Finally, we reexamine the optimal size of buffer stocks, showing that disappointment aversion increases its size by a first order magnitude. A buffer stock that is rather small when agents are maximizing the conventional expected utility is rather large when agents are disappointment averse.

    Wage Flexibility and Openness

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    This paper analyzes the degree of short-run, real wage flexibility in a two-sector economy under floating rates. This is done by deriving optimal wage indexation in a contracting framework. We find that the more closed the economy, the lower the degree of wage indexation. As a result, output will fluctuate less around its desired level in a more closed economy. These findings further imply that a given unexpected monetary shock will cause as maller output shock in a more open economy, whereas a given real shock will induce a smaller output shock in a more closed economy.

    Capital Controls and Financial Crises

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    The purpose of this paper is to explain the reluctance of developing countries to open up their capital market to foreigners, and the conditions inducing an emerging market economy to switch its policies. We consider an economy characterized initially by a one-sided openness to the capital market domestic agents can borrow internationally, but foreign agents cannot hold domestic equity. We identify conditions under which the emerging market's capitalists would oppose financial reform. This would be the case if 'green field' investment by multinationals would bid up real wages, reducing thereby the rents of domestic capitalists. A financial crisis that raises the domestic interest rate and causes a real exchange rate depreciation may induce the emerging market's capitalists to support opening up the economy to FDI. This attitude switch is more likely to occur the greater the debt overhang, the lower the borrowing constraint, and the weaker the market power of foreign entrepreneurs. Even in these circumstances, the emerging market's capitalists would prefer a partial reform to a comprehensive one -- they would prefer to maintain the restrictions on 'green field' FDI.

    Volatility, employment and the patterns of FDI in emerging markets

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    The purpose of this paper is to explore the implications of the deepening presence of multinationals in emerging markets on the cost of macroeconomic volatility there. We find that macroeconomic volatility has a potentially large impact on employment and investment decisions of multinationals producing intermediate inputs in developing countries. This is the case even for risk neutral multinationals, as their profit function is non-linear due to price and productivity effects. For industries with costly capacity, the multinationals would tend to invest in the more stable emerging markets. Higher volatility of productivity shocks in an emerging market producing the intermediate inputs reduces the multinationals' expected profits. High enough instability in such a market would induce the multinationals to diversify intermediate inputs production, investing in several emerging markets. This effect is stronger in lower margin industries. We identify circumstances where this diversification is costly to emerging markets. Such a diversification increases the responsiveness of the multinationals' employment in each country to productivity shocks, channeling the average employment from the more to the less volatile location, and reducing the multinationals' total expected employment in emerging markets.

    Exchange Rate Flexibility, Volatility, and the Patterns of Domestic and Foreign Direct Investment

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    The goal of this paper is to investigate the factors determining the impact of exchange rate regimes on the behavior of domestic investment and foreign direct investment (FDI), and the correlation between exchange rate volatility and investment. We assume that producers may diversify internationally in order to increase the flexibility of production: being a multinational enables producers to reallocate employment and production towards the more efficient or the cheaper plant. We characterize the possible equilibria in a macro model that allows for the presence of a short-run Phillips curve, under a fixed and a flexible exchange rate regime. It is shown that a fixed exchange rate regime is more conducive to FDI relative to a flexible exchange rate, and this conclusion applies for both real and nominal shocks. The correlation between investment and exchange rate volatility under a flexible exchange rate is shown to depend on the nature of the shocks. If the dominant shocks are nominal, we will observe a negative correlation, whereas if the dominant shocks are real, we will observe a positive correlation between exchange rate volatility and the level of investment.

    Financial Opening: Evidence and Policy Options

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    This paper evaluates the empirical evidence of increasing the chances of financial crises induced by opening up developing countries to short-term capital inflows, and appraises the various proposals made for mitigating the severity of financial crises. We point out that there is solid evidence that financial opening increases the chance of financial crises. There is more tenuous evidence that financial opening contributes positively to long-run growth. Hence, there may be a complex trade off between the adverse intermediate run and the beneficial long run effects of financial opening. The literature is abounded with proposals aimed at improving this intertemporal trade-off, reducing the costs of financial crises. A version of the Lucas critic may limit the welfare gain of these proposals. Hence, a better understanding of the structural characteristics leading to exposure and crises is the key for designing a successful restructuring of the global capital market. Some of the reforms may fall short of success due to coordination failure: they may be effective only if they were adopted comprehensively by all the relevant financial centers. Finally, some of the proposals may be too optimistic, ignoring the time inconsistency and political economy considerations, as well as presuming the ability to verify unambiguously the quality of adjustment.
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