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We study a problem of optimal influence in a society where agents learn from their neighbors. We consider a firm that seeks to maximize the diffusion of a new product whose quality is ex–ante uncertain, to a market where consumers are able to compare the qualities of two alternative products as soon as they observe both of them. The firm can seed the product to a subset of the population and our goal is to find which is the optimal subset to target. We provide a necessary and sufficient condition that fully characterizes the optimal targeting strategy for any network structure. The key parameter in this condition is the agents’ decay centrality, which is a measure that takes into account how close an agent is to others, but in a way that very distant agents are weighted less than closer ones.

We analyze the impact of the immigration influx that took place during the years 2000-2007 in Greece on labor market outcomes. We employ a search and matching framework that allows for skill heterogeneity and differential unemployment income (search cost) between immigrants and natives. Within such a framework, we find that skilled native workers, who complement immigrants in production, gain in terms of both wages and employment. The effects on unskilled native workers, who compete with immigrants, on the other hand, are ambiguous and depend first on the presence of a statutory minimum wage and second on the way that this minimum wage is determined. © 2013 Elsevier Inc. 19-34 38 19 34

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Over the last four decades, a large number of structural models have been developed to estimate and price credit risk. The focus of the paper is on a neglected issue pertaining to fundamental shifts in the structural parameters governing default. We propose formal quality control procedures that allow risk managers to monitor fundamental shifts in the structural parameters of credit risk models. The procedures are sequential - hence apply in real time. The basic ingredients are the key processes used in credit risk analysis, such as most prominently the Merton distance to default process as well as financial returns. Moreover, while we propose different monitoring processes, we also show that one particular process is optimal in terms of minimal detection time of a break in the drift process and relates to the Radon-Nikodym derivative for a change of measure. © 2008 Elsevier B.V. All rights reserved. 364-375 375 364 146

In this paper, we empirically examine the portfolio-rebalancing effects stemming from the policy of "quantitative monetary easing" recently undertaken by the Bank of Japan when the nominal short-term interest rate was virtually at zero. Portfolio-rebalancing effects resulting from the open market purchase of long-term government bonds under this policy have been statistically significant. Our results also show that the portfolio-rebalancing effects were beneficial in that they reduced risk premiums on assets with counter-cyclical returns, such as government and high-grade corporate bonds. But, they may have generated the adverse effects of increasing risk premiums on assets with pro-cyclical returns, such as equities and low-grade corporate bonds. These results are consistent with a CAPM framework in which business-cycle risk importantly affects risk premiums. Our estimates capture only some of the effects of quantitative easing and thus do not imply that the complete set of effects were adverse on net for Japan's economy. However, our analysis counsels caution in accepting the view that, ceteris paribus, a massive large-scale purchase of long-term government bonds by a central bank provides unambiguously positive net benefits to financial markets at zero short-term interest rates.