Andrada Bilan, Yalin Gunduz, CDS Market Liquidity and Bond Spreads , In: -, No. -, 2019. (Working Paper)
This paper studies the effects of a supply shock to the liquidity of credit default swap (CDS) markets on bond spreads. Using as a laboratory the universe of CDS transactions done by German banks, our model is identified by changes in CDS market liquidity due to the exit of a large dealer. We find that the CDS market converges to a new equilibrium, where traded volumes are lower and bid-ask spreads are higher. Bond yields increase in response, with stronger effects for the non-investment-grade class. Individual portfolio data indicate that the effect is partly driven by investors decreasing their holdings of both CDS and related bonds. We, therefore, show that derivative markets can affect demand in underlying securities and, subsequently, the issuers’ cost of capital. |
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Silvia Maier, Todd Anthony Hare, Greater BOLD signal during successful emotional stimulus reappraisal is associated with better dietary self-control, In: bioRxiv, No. 542712, 2019. (Working Paper)
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Michael A. Ribers, Hannes Ullrich, Battling Antibiotic Resistance: Can Machine Learning Improve Prescribing?, In: SSRN, No. 3392196, 2019. (Working Paper)
Antibiotic resistance constitutes a major health threat. Predicting bacterial causes of infections is key to reducing antibiotic misuse, a leading cause of antibiotic resistance. We combine administrative and microbiological laboratory data from Denmark to train a machine learning algorithm predicting bacterial causes of urinary tract infections. Based on predictions, we develop policies to improve prescribing in primary care, highlighting the relevance of physician expertise and time-variant patient distributions for policy implementation. The proposed policies delay prescriptions for some patients until test results are known and give them instantly to others. We find that machine learning can reduce antibiotic use by 7.42 percent without reducing the number of treated bacterial infections. As Denmark is one of the most conservative countries in terms of antibiotic use, targeting a 30 percent reduction in prescribing by 2020, this result is likely to be a lower bound of what can be achieved elsewhere. |
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Steven Ongena, Sascha Kolaric, Florian Kiesel, Market discipline through credit ratings and Too-Big-To-Fail in banking, In: Swiss Finance Institute Research Paper, No. 17-09, 2020. (Working Paper)
Do credit ratings help enforce market discipline on banks? Analyzing a uniquely comprehensive dataset consisting of 1,081 rating change announcements for 154 international financial institutions between January 2004 and December 2015, we find that rating downgrades for internal reasons, such as adverse changes in the operating performance or capital structure of banks, are associated with a significant CDS spread widening. However, this widening only occurs for banks that are not perceived as to be Too-Big-to-Fail (TBTF). Our findings question the reliability of credit ratings as a tool to discipline TBTF banks and suggest that regulatory monitoring should remain the main mechanism for disciplining these banks. |
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Andrada Bilan, Yalin Gunduz, When Big Banks Exit OTC Markets: Liquidity, Prices, and Spillover Effects, In: -, No. -, 2019. (Working Paper)
This paper studies the real effects of a change in the dealer composition in OTC markets. Using as a laboratory the universe of CDS transactions entered into by German banks and the exit of a large dealer in November 2014 as a shock, we first show that the CDS market converges to a new equilibrium, with lower traded volumes and higher bid-ask spreads. Using individual portfolios we find that in response investors rebalance both their CDS holdings and bond portfolios. In particular, CDS protection buyers decrease their holdings of the bonds underlying CDS contracts. The effects are strongest for non-investment grade bonds. We therefore show that the exit of large dealers from OTC markets could affect investor demand in related securities and, in consequence, the issuers cost of capital. |
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Andrada Bilan, Luciana Barbosa, Claire Célérier, Capital Inflows, Credit Growth and Skill (Mis)allocation, In: ECB Working Paper, No. 2271, 2019. (Working Paper)
In emerging markets and Southern Europe, large capital inflows have led to a decrease in the allocative efficiency of capital. Do capital inflows also affect the allocation of workers and skills? To address this question, we exploit exogenous variations in Portuguese banks' ability to channel capital inflows over the 2002-2007 period. Using comprehensive bank-firm-employee data, we show that not only leverage, but also employment and skill-intensity increase in firms exposed to bank-channeled capital inflows. |
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Luca Mazzone, On the Solution of High-Dimensional Macro Models with Distributional Channels, In: Swiss Finance Institute Research Paper, No. 19-01, 2019. (Working Paper)
Importance of distributional channels in macroeconomic dynamics has been the object of considerable attention in empirical studies. Despite significant amount of effort aimed at incorporating heterogeneity into macroeconomics, however, their explicit inclusion in the standard policy toolbox is far from widespread. A relevant obstacle, in such cases, is the computation of equilibria. I propose a global solution method for the computation of infinite-horizon, heterogeneous agent macroeconomic models with aggregate uncertainty. Details of the algorithm are illustrated by presenting its application to a an example model: in it, aggregate dynamics depends explicitly on firm entry and exit, and individual choices are often constrained by a form of market incompleteness. Existing computational strategies are either unfeasible or provide inaccurate solutions. Moreover, global solutions are computationally expensive because the minimal representation of the aggregate state space - and thus the aggregate law of motion - faces the curse of dimensionality. The proposed strategy thus combines adaptive sparse grids with a cross-sectional density approximation, and introduces a framework for solving the more general class of dynamic models with firm or household heterogeneity accurately. |
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Luca Rossetto, Ralph Gasser, Heiko Schuldt, Query by Semantic Sketch, In: ArXiv.org, No. :1909.1252, 2019. (Working Paper)
Sketch-based query formulation is very common in image and video retrieval as these techniques often complement textual retrieval methods that are based on either manual or machine generated annotations. In this paper, we present a retrieval approach that allows to query visual media collections by sketching concept maps, thereby merging sketch-based retrieval with the search for semantic labels. Users can draw a spatial distribution of different concept labels, such as "sky", "sea" or "person" and then use these sketches to find images or video scenes that exhibit a similar distribution of these concepts. Hence, this approach does not only take the semantic concepts themselves into account, but also their semantic relations as well as their spatial context. The efficient vector representation enables efficient retrieval even in large multimedia collections. We have integrated the semantic sketch query mode into our retrieval engine vitrivr and demonstrated its effectiveness. |
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Selin Akca, Anita Rao, Value of Search Aggregators, In: SSRN, No. 3064861, 2019. (Working Paper)
Aggregators are facing increased scrutiny by regulatory authorities, suggesting these sites have considerable market power. On the other extreme, firms are bypassing aggregators, choosing instead to sell directly to consumers. This raises the question as to which party has more market power: the aggregator or the individual firm. Focusing on the airline industry, we investigate who benefits the most in the airline-aggregator relationship. Specifically, we ask what would happen to airline and aggregator site visits and purchases in the absence of a comprehensive aggregator. We first explore consumers’ search patterns on Southwest, an airline that has never been part of any aggregator. In a descriptive exercise, we find that consumers who book on Southwest are the least likely to visit aggregator sites. Second, we use the 2011 American dispute with Orbitz as an exogenous event, which led to American fares no longer being displayed on Orbitz for five months. We use this dispute to identify who was hurt the most – the aggregator or the airline - in the months following the dispute. Our findings indicate the aggregator loses the most when it is not comprehensive. |
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Luis Aguiar, Joel Waldfogel, Digitization, Copyright, and the Welfare Effects of MusicTrade, In: Scientific and Technical Research series, No. 5, 2014. (Working Paper)
Since the launch of the iTunes Music Store in the US in 2003 and in much of Europe in the following years, music trade has shifted rapidly from physical to digital products, raising the availability of products in different countries. Despite substantial growth in availability, choice sets have not converged across countries; and observers point to copyright-related transaction costs as an obstacle to greater availability. Policy makers are now contemplating various copyright reforms that could reduce these trade costs. The possibility of these changes raises the question of how much benefit they would create for consumers and producers around the world. We address these questions with a structural model of supply and demand for music in 17 countries, which we employ to counterfactually simulate the effect of a European digital single market on the welfare of consumers and producers. We also simulate autarky and worldwide frictionless trade - in which all products are available in all countries - allowing us to quantify both the conventional gains from status quo trade as well as the maximum possible gains available to free trade. Existing and additional trade have different patterns of benefit to consumers and producers. Status quo trade benefits consumers everywhere, but European consumers have benefited more than North Americans. Existing trade has had large benefits to American producers but on balance small benefits to European producers. Additional trade would continue the pattern of consumers' benefits with larger gains to European consumers but would reverse the pattern for producers. Greater availability of digital music resulting from easing of copyright restrictions would raise per capita gains to producers in Europe more than in North America. A Europeandigital single market for music would bring total benefits of €19 million to European consumers and €10 million to European producers. Finally, we find that a European digital single market would bring most of the benefits of worldwide frictionless trade to both consumers and producers alike. |
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Luis Aguiar, Joel Waldfogel, Platforms, Promotion, and Product Discovery: Evidence from Spotify Playlists, In: NBER Working Paper Series, No. 24713, 2018. (Working Paper)
Digitization has vastly increased the amount of new music produced and available directly to consumers. While this has levelled the playing field between already-prominent and new artists, creators maynow be dependent on platform decisions about which songs and artist to promote. With Spotify emergingas a major interactive streaming platform, this paper explores the effect of Spotify’s playlists on boththe promotion of songs and the discovery of music by new artists, using four approaches. First, weexamine songs’ streaming volumes before and after their addition to, and removal from, major globalplaylists. Second, we compare streaming volumes for songs just on, and just off, algorithmic top 50 playlists. Third, we make use of cross-country differences in inclusion on New Music Friday lists,using song fixed effects to explain differences in streaming. Fourth, we develop an instrumental variables approach to explaining cross-country New Music Friday rank differentials based on home bias. Beingadded to Today’s Top Hits, a list with 18.5 million followers during the sample period, raises streams by almost 20 million and is worth between 116,000 Dollar and 163,000 Dollar. Inclusion on New Music Friday lists substantially raises the probability of song success, including for new artists. |
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Cédric Chambru, Weather shocks, poverty and crime in 18th-century Savoy, In: Economic History Working Papers, No. 1/2019, 2019. (Working Paper)
Did weather shocks increase interpersonal conflict in early modern Europe? I address this question by exploiting year-to-year seasonal variations in temperature and detailed crime data I assembled from Savoyard criminal procedures over the period 1749--89. I find that temperature shocks had a positive and significant effect on the level of property crimes, but no significant effect on violent crimes. I further document how seasonal migration may help to increase the coping capacity of local communities in which they were widely used. Migrant labourers brought remittances to supplement communities' resources and also temporarily relieve their communities of the burden of feeding them. I show that temperature shocks were strongly associated with increase in the property crimes rate, but the effect is much lower in provinces with high levels of seasonal migration. I provide historical evidence to show that the inflow of remittances may drive this relationship. |
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Albert Solé-Ribalta, Claudio Tessone, Carlo Ferrari, Javie Borge-Holthoefer, Disentangling co-occurrence patterns in n-partite ecosystems, In: ArXiv.org, No. 1810.12785, 2018. (Working Paper)
The need to harmonise apparently irreconcilable arrangements in an ecosystem –nestedness andsegregation– has triggered so far different strategies. Methodological refinements, or the inclusion ofbehavioural preferences to the network dynamics offer a limited approach to the problem, since oneremains constrained within a 2-dimensional view of an ecosystem, i.e. a presence-absence matrix.Here we question this partial-view paradigm, and show that nestedness and segregation may coexistacross a varied range of scenarios. To do so, we rely on an upscaled representation of an ecologicalcommunity as ann-partite hypergraph, inspired by Hutchinson’s high-dimensional niche conceptand the latest trends on ecological multilayer networks. This yields an inclusive description of anecological system, for which we develop a natural extension of the definition of nestedness to largerdimensional spaces, revealing how competitive exclusion may operate regardless of a highly nestedbipartite system. |
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María J Palazzi, Javier Borge-Holthoefer, Claudio Tessone, Albert Solé-Ribalta, Antagonistic structural patterns in complex networks, In: ArXiv.org, No. 1810.12785, 2018. (Working Paper)
Identifying and explaining the structure of complex networks at different scales has become an important problem across disciplines. At the mesoscale, modular architecture has attracted most of the attention. At the macroscale, other arrangements --e.g. nestedness or core-periphery-- have been studied in parallel, but to a much lesser extent. However, empirical evidence increasingly suggests that characterizing a network with a unique pattern typology may be too simplistic, since a system can integrate properties from distinct organizations at different scales. Here, we explore the relationship between some of those organizational patterns: two at the mesoscale (modularity and in-block nestedness); and one at the macroscale (nestedness). We analytically show that nestedness can be used to provide approximate bounds for modularity, with exact results in an idealized scenario. Specifically, we show that nestedness and modularity are antagonistic. Furthermore, we evince that in-block nestedness provides a parsimonious transition between nested and modular networks, taking properties of both. Far from a mere theoretical exercise, understanding the boundaries that discriminate each architecture is fundamental, to the extent modularity and nestedness are known to place heavy constraints on the stability of several dynamical processes, specially in ecology. |
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Alexandre Bovet, Carlo Campajola, Francesco Mottes, Valerio Restocchi, Nicolò Vallarano, Tiziano Squartini, Claudio Tessone, The evolving liaisons between the transaction networks of Bitcoin and its price dynamics, In: ArXiv.org, No. 1907.03577, 2019. (Working Paper)
Cryptocurrencies are distributed systems that allow exchanges of native tokens among par-ticipants, or the exchange of such tokens for fiat currencies in markets external to these public ledgers. The availability of their complete historical bookkeeping opens up the possibility of understanding the relationship between aggregated users’ behaviour and the cryptocur-rency pricing in exchange markets. This paper analyses the properties of the transaction network of Bitcoin. We consider four different representations of it, over a period of nine years since the Bitcoin creation and involving 16 million users and 283 million transactions. By analysing these networks, we show the existence of causal relationships between Bitcoin price movements and changes of its transaction network topology. Our results reveal the in-terplay between structural quantities, indicative of the collective behaviour of Bitcoin users, and price movements, showing that, during price drops, the system is characterised by a larger heterogeneity of nodes activity. |
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Gazi Kabas, Sebastian Klaus Dörr, Banking On Demography: Population Aging and Financial Integration, In: SSRN, No. 3430184, 2019. (Working Paper)
This paper argues that an integrated financial sector mitigates negative effects of population aging. We show that U.S. counties with an aging population see an increase in local deposits, reflecting higher saving rates of seniors. Banks use these deposits to increase credit supply. Using detailed data on mortgage lending, we find that banks channel deposits from aging counties towards counties with a younger population. We find no evidence that banks engage in risky lending: they lend less to counties with a high share of sub-prime borrowers or low incomes, and do not lend disproportionately to low-income borrowers. The increase in credit supply has real effects. Counties with a higher market share of aging-exposed banks see an increase in house prices and building permits, as well as in firm formation. Results are robust to controlling for bank and county characteristics through granular fixed effects and instrumenting local aging with casualties during World War II. |
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Nils Kristof Olberg, Sven Seuken, Enabling Trade-offs in Machine Learning-based Matching for Refugee Resettlement, In: -, No. -, 2019. (Working Paper)
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Peter Gordon Rötzel, Alexander Stehle, Burkhard Pedell, Katrin Hummel, Integrating environmental management control systems to translate environmental strategy into managerial performance, In: SSRN, No. 1, 2019. (Working Paper)
This study investigates the role of environmental management control systems as mechanisms to translate environmental strategy into environmental managerial performance. While prior research focuses primarily on environmental performance at the organizational level, this study specifically addresses individual managerial performance with regard to environmental outcomes. In addition, we investigate how the level of integration between regular and environmental management control systems influences the relation between environmental strategy and environmental managerial performance as well as the mediating role of environmental management control systems. Based on survey data from 218 firms and structural equation modeling, the results show that environmental management control systems mediate the relationship between environmental strategy and environmental managerial performance. Moreover, the level of integration significantly impacts the relationship between environmental management control systems and environmental managerial performance. Therefore, environmental management control systems are important mechanisms to translate environmental strategy into managerial performance, and a high level of integration can reinforce this role. |
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Vincenzo Perri, Ingo Scholtes, Higher-Order Visualization of Causal Structures in Dynamics Graphs, In: ArXiv.org, No. 1908.05976, 2019. (Working Paper)
Graph or network representations are an important foundation for data mining and machine learning tasks in relational data. Many tools of network analysis, like centrality measures, information ranking, or cluster detection rest on the assumption that links capture direct influence, and that paths represent possible indirect influence. This assumption is invalidated in time-stamped network data capturing, e.g., dynamic social networks, biological sequences or financial transactions. In such data, for two time-stamped links (A,B) and (B,C) the chronological ordering and timing determines whether a causal path from node A via B to C exists. A number of works has shown that for that reason network analysis cannot be directly applied to time-stamped network data. Existing methods to address this issue require statistics on causal paths, which is computationally challenging for big data sets.
Addressing this problem, we develop an efficient algorithm to count causal paths in time-stamped network data. Applying it to empirical data, we show that our method is more efficient than a baseline method implemented in an OpenSource data analytics package. Our method works efficiently for different values of the maximum time difference between consecutive links of a causal path and supports streaming scenarios. With it, we are closing a gap that hinders an efficient analysis of big time series data on complex networks. |
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Luka Petrovic, Ingo Scholtes, Counting Causal Paths in Big Time Series Data on Networks, In: ArXiv.org, No. 1905.11287, 2019. (Working Paper)
Graph or network representations are an important foundation for data mining and machine learning tasks in relational data. Many tools of network analysis, like centrality measures, information ranking, or cluster detection rest on the assumption that links capture direct influence, and that paths represent possible indirect influence. This assumption is invalidated in time-stamped network data capturing, e.g., dynamic social networks, biological sequences or financial transactions. In such data, for two time-stamped links (A,B) and (B,C) the chronological ordering and timing determines whether a causal path from node A via B to C exists. A number of works has shown that for that reason network analysis cannot be directly applied to time-stamped network data. Existing methods to address this issue require statistics on causal paths, which is computationally challenging for big data sets.
Addressing this problem, we develop an efficient algorithm to count causal paths in time-stamped network data. Applying it to empirical data, we show that our method is more efficient than a baseline method implemented in an OpenSource data analytics package. Our method works efficiently for different values of the maximum time difference between consecutive links of a causal path and supports streaming scenarios. With it, we are closing a gap that hinders an efficient analysis of big time series data on complex networks. |
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