Systemic risk, here meant as the risk of default of a large portion of the financial system, depends on the network of financial exposures among institutions. However, there is no widely accepted methodology to determine the systemically important nodes in a network. To fill this gap, we introduce, DebtRank, a novel measure of systemic impact inspired by feedback-centrality. As an application, we analyse a new and unique dataset on the USD 1.2 trillion FED emergency loans program to global financial institutions during 2008–2010. We find that a group of 22 institutions, which received most of the funds, form a strongly connected graph where each of the nodes becomes systemically important at the peak of the crisis. Moreover, a systemic default could have been triggered even by small dispersed shocks. The results suggest that the debate on too-big-to-fail institutions should include the even more serious issue of too-central-to-fail.
The paper provides basic concepts about Blockchain and offers our perspective on the challenges, the future opportunities and the foreseeable impact of Blockchain and distributed ledger technologies in industry and society. The origins of this technologies are tracked, from the Bitcoin digital cash system to more recent applications. Additional possible usages of Blockchain and distributed ledger technologies in other domains are covered by highlighting potentials but also weaknesses, limitations and risks.Draft NOT for distribution, to be published on IEEE 2017
A comparative study across the most widely known blockchain technologies is conducted with a bottom-up approach. Blockchains are disentangled into building blocks. Each building block is then hierarchically classified in main and subcomponents. Then, alternative layouts for the subcomponents are identified and compared between them. Finally, a taxonomy tree summarises the study and provides a navigation tool across different blockchain architectural configurations.The solution to these problems requires the setting up of software reference architectures where standardised structures and respective elements and relations shall provide templates for concrete blockchain architectures. Standards can emerge naturally because of market adoption (industry driven) or because imposed by institutes and organisations. In the first group we may include initiatives like the Accord Project 1 , the ChinaLedger 2 or R3 3 . In the second group we may refer to the initiative conducted by the International Organization for Standardization (ISO) with the establishment of the technical committee ISO/TC 307 on Blockchain and distributed ledger technologies. Several working groups with different topics to discuss have been settled. In particular, the ISO/TC 307/WG1 working group is engaged with the reference architecture, taxonomy and ontology. Overall, a long-term standardisation of the blockchain reference architecture will benefit every industry. Thus, a standard for software reference architecture is necessary in order to enable a level playing field where every industry player and community member can design and adopt blockchainenabled products or services under the same very conditions with possibility of data exchange. As it is for the Internet, several institutes of standardisations (e.g., ETF in cooperation with the W3C, ISO/IEC, ITU) set a body of standards. Internet standards promote interoperability of systems on the Internet by defining precise protocols, message formats, schemas, and languages. As a result, different hardware and software can seamlessly interact and work together. Applied to World Wide Web (as a layer on the top of the Internet), standards bring interoperability, accessibility and usability of web pages. Similarly, the adoption of blockchain standards will promote the blossoming and proliferation of interoperable blockchain-enabled applications. Thus, if we envisage a future where blockchains will be one of the pillars of our society's development, it is necessary to begin discussing and identifying standards for blockchain reference architectures. The aim of this study is to highlight the need for standard technical reference models of blockchain architectures. This is timely aligned with the industry sentiment which currently pushes organisations for standardisation to set industry standards. In order to support an appropriate co-regulatory framework for blockchain-related industries, a multi-party approach is necessary as it is for the Internet where both national standards, international standards and...
In this paper, we gather together the minimum units of Bitcoin identity (the individual addresses), and group them into approximations of business entities, what we call "super clusters". While these clusters can remain largely anonymous, we are able to ascribe many of them to particular business categories by analyzing some of their specific transaction patterns, as observed during the period from 2009-2015. We are then able to extract and create a map of the network of payment relationships among them, and analyze transaction behavior found in each business category. We conclude by identifying three marked regimes that have evolved as the Bitcoin economy has grown and matured: from an early prototype stage; to a second growth stage populated in large part with "sin" enterprise (i.e., gambling, black markets); to a third stage marked by a sharp progression away from "sin" and toward legitimate enterprises.
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