Systemic Risk in a Unifying Framework for Cascading Processes on Networks

We introduce a general framework for models of cascade and contagion processes on networks, to identify their commonalities and differences. In particular, models of social and financial cascades, as well as the fiber bundle model, the voter model, and models of epidemic spreading are recovered as special cases. To unify their description, we define the net fragility of a node, which is the difference between its fragility and the threshold that determines its failure. Nodes fail if their net fragility grows above zero and their failure increases the fragility of neighbouring nodes, thus possibly triggering a cascade. In this framework, we identify three classes depending on the way the fragility of a node is increased by the failure of a neighbour. At the microscopic level, we illustrate with specific examples how the failure spreading pattern varies with the node triggering the cascade, depending on its position in the network and its degree. At the macroscopic level, systemic risk is measured as the final fraction of failed nodes, $X^\ast$, and for each of the three classes we derive a recursive equation to compute its value. The phase diagram of $X^\ast$ as a function of the initial conditions, thus allows for a prediction of the systemic risk as well as a comparison of the three different model classes. We could identify which model class lead to a first-order phase transition in systemic risk, i.e. situations where small changes in the initial conditions may lead to a global failure. Eventually, we generalize our framework to encompass stochastic contagion models. This indicates the potential for further generalizations.Comment: 43 pages, 16 multipart figure

Priority for the Worse Off and the Social Cost of Carbon

The social cost of carbon (SCC) is a monetary measure of the harms from carbon emission. Specifically, it is the reduction in current consumption that produces a loss in social welfare equivalent to that caused by the emission of a ton of CO2. The standard approach is to calculate the SCC using a discounted-utilitarian social welfare function (SWF)—one that simply adds up the well-being numbers (utilities) of individuals, as discounted by a weighting factor that decreases with time. The discounted-utilitarian SWF has been criticized both for ignoring the distribution of well-being, and for including an arbitrary preference for earlier generations. Here, we use a prioritarian SWF, with no time-discount factor, to calculate the SCC in the integrated assessment model RICE. Prioritarianism is a well-developed concept in ethics and theoretical welfare economics, but has been, thus far, little used in climate scholarship. The core idea is to give greater weight to well-being changes affecting worse off individuals. We find substantial differences between the discounted-utilitarian and non-discounted prioritarian SCC

A kinetic equation for economic value estimation with irrationality and herding

A kinetic inhomogeneous Boltzmann-type equation is proposed to model the dynamics of the number of agents in a large market depending on the estimated value of an asset and the rationality of the agents. The interaction rules take into account the interplay of the agents with sources of public information, herding phenomena, and irrationality of the individuals. In the formal grazing collision limit, a nonlinear nonlocal Fokker-Planck equation with anisotropic (or incomplete) diffusion is derived. The existence of global-in-time weak solutions to the Fokker-Planck initial-boundary-value problem is proved. Numerical experiments for the Boltzmann equation highlight the importance of the reliability of public information in the formation of bubbles and crashes. The use of Bollinger bands in the simulations shows how herding may lead to strong trends with low volatility of the asset prices, but eventually also to abrupt corrections

Economic Activity of Firms and Asset Prices

In this review we survey the recent research on the fundamental determinants of stock returns. These studies explore how firms' systematic risk and their investment and production decisions are jointly determined in equilibrium. Models with production provide insights into several types of empirical patterns, including (a) the correlations between firms' economic characteristics and their risk premia, (b) the comovement of stock returns among firms with similar characteristics, and (c) the joint dynamics of asset returns and macroeconomic quantities. Moreover, by explicitly relating firms' stock returns and cash flows to fundamental shocks, models with production connect the analysis of financial markets with the research on the origins of macroeconomic fluctuations

Booms and busts in commodity markets: bubbles or fundamentals?

This paper considers whether there were periodically collapsing rational speculative bubbles in commodity prices over a 40-year period from the late 1960s. We apply a switching regression approach to a broad range of commodities using two different measures of fundamental values—estimated from convenience yields and from a set of macroeconomic factors believed to affect commodity demand. We find reliable evidence for bubbles only among crude oil and feeder cattle, showing the popular belief that the extreme price movements observed in commodity markets were caused by pure speculation to be unsustainabl

Explaining co-movements between equity and CDS bid-ask spreads

In this paper I show that the co-movements between bid-ask spreads of equities and credit default swaps vary over time and increase over crisis periods. The co-movements are strongly related to systematic risk factors and to the theoretical debt-to-equity hedge ratio. I document that hedging and asymmetric information, besides higher funding costs and market volatility risk, are driving factors of the commonality and are significantly priced in CDS bid-ask spreads

Resources, Capabilities, and Routines in Public Organizations

States, state agencies, multilateral agencies, and other non-market actors are relatively under-studied in strategic management and organization science. While important contributions to the study of public actors have been made within the agency-theoretic and transaction-cost traditions, there is little research in political economy that builds on resource-based, dynamic capabilities, and behavioral approaches to the firm. Yet public organizations can be characterized as stocks of human and non-human resources, including routines and capabilities; they can possess excess capacity in these resources; and they may grow and diversify in predictable patterns according to behavioral and Penrosean logic. This paper shows how resource-based, dynamic capabilities, and behavioral approaches to understanding public agencies and organizations shed light on their nature and governance

Bank Heterogeneity and Capital Allocation: Evidence from 'Fracking' Shocks

This paper empirically investigates banks' investment allocations over the recent business cycle. I identify unsolicited deposit shocks resulting from unconventional energy development and estimate bank allocations of these deposits. In the pre-recession period, banks lend 38 percent of incremental deposits; however, during the downturn, banks favor liquid assets and lending allocations fall to 22 percent. Banks with low risk tolerance or less access to liquidity are particularly sensitive to the decline in economic conditions, choosing securities and cash, respectively. The findings identify significant heterogeneity in the willingness of banks to allocate capital during adverse times

Dynamic Provisioning: Some Lessons from Existing Experiences

After analyzing the different reasons why the financial system and also the regulatory framework induced procyclicality, this paper reviews the experiences of three countries which have introduced dynamic provisioning as a regulatory tool to limit procyclicality. The case of Spain - the country with the longest experience - is reviewed, as well as those of Colombia and Peru - countries that have recently adopted dynamic provisioning. A number of policy lessons are drawn from that comparison