Efficient pricing algorithms for exotic derivatives

Download Efficient pricing algorithms for exotic derivatives PDF Online Free

Author :
Publisher : Rozenberg Publishers
ISBN 13 : 9051709099
Total Pages : 211 pages
Book Rating : 4.0/5 (517 download)

DOWNLOAD NOW!


Book Synopsis Efficient pricing algorithms for exotic derivatives by : Roger Lord

Download or read book Efficient pricing algorithms for exotic derivatives written by Roger Lord and published by Rozenberg Publishers. This book was released on 2008 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Modelling and Simulation of Stochastic Volatility in Finance

Download Modelling and Simulation of Stochastic Volatility in Finance PDF Online Free

Author :
Publisher : Universal-Publishers
ISBN 13 : 1581123833
Total Pages : 219 pages
Book Rating : 4.5/5 (811 download)

DOWNLOAD NOW!


Book Synopsis Modelling and Simulation of Stochastic Volatility in Finance by : Christian Kahl

Download or read book Modelling and Simulation of Stochastic Volatility in Finance written by Christian Kahl and published by Universal-Publishers. This book was released on 2008 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: The famous Black-Scholes model was the starting point of a new financial industry and has been a very important pillar of all options trading since. One of its core assumptions is that the volatility of the underlying asset is constant. It was realised early that one has to specify a dynamic on the volatility itself to get closer to market behaviour. There are mainly two aspects making this fact apparent. Considering historical evolution of volatility by analysing time series data one observes erratic behaviour over time. Secondly, backing out implied volatility from daily traded plain vanilla options, the volatility changes with strike. The most common realisations of this phenomenon are the implied volatility smile or skew. The natural question arises how to extend the Black-Scholes model appropriately. Within this book the concept of stochastic volatility is analysed and discussed with special regard to the numerical problems occurring either in calibrating the model to the market implied volatility surface or in the numerical simulation of the two-dimensional system of stochastic differential equations required to price non-vanilla financial derivatives. We introduce a new stochastic volatility model, the so-called Hyp-Hyp model, and use Watanabe's calculus to find an analytical approximation to the model implied volatility. Further, the class of affine diffusion models, such as Heston, is analysed in view of using the characteristic function and Fourier inversion techniques to value European derivatives.

Pricing Models of Volatility Products and Exotic Variance Derivatives

Download Pricing Models of Volatility Products and Exotic Variance Derivatives PDF Online Free

Author :
Publisher : CRC Press
ISBN 13 : 1000584259
Total Pages : 283 pages
Book Rating : 4.0/5 (5 download)

DOWNLOAD NOW!


Book Synopsis Pricing Models of Volatility Products and Exotic Variance Derivatives by : Yue Kuen Kwok

Download or read book Pricing Models of Volatility Products and Exotic Variance Derivatives written by Yue Kuen Kwok and published by CRC Press. This book was released on 2022-05-08 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pricing Models of Volatility Products and Exotic Variance Derivatives summarizes most of the recent research results in pricing models of derivatives on discrete realized variance and VIX. The book begins with the presentation of volatility trading and uses of variance derivatives. It then moves on to discuss the robust replication strategy of variance swaps using portfolio of options, which is one of the major milestones in pricing theory of variance derivatives. The replication procedure provides the theoretical foundation of the construction of VIX. This book provides sound arguments for formulating the pricing models of variance derivatives and establishes formal proofs of various technical results. Illustrative numerical examples are included to show accuracy and effectiveness of analytic and approximation methods. Features Useful for practitioners and quants in the financial industry who need to make choices between various pricing models of variance derivatives Fabulous resource for researchers interested in pricing and hedging issues of variance derivatives and VIX products Can be used as a university textbook in a topic course on pricing variance derivatives

Topics in Numerical Methods for Finance

Download Topics in Numerical Methods for Finance PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 1461434335
Total Pages : 213 pages
Book Rating : 4.4/5 (614 download)

DOWNLOAD NOW!


Book Synopsis Topics in Numerical Methods for Finance by : Mark Cummins

Download or read book Topics in Numerical Methods for Finance written by Mark Cummins and published by Springer Science & Business Media. This book was released on 2012-07-15 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting state-of-the-art methods in the area, the book begins with a presentation of weak discrete time approximations of jump-diffusion stochastic differential equations for derivatives pricing and risk measurement. Using a moving least squares reconstruction, a numerical approach is then developed that allows for the construction of arbitrage-free surfaces. Free boundary problems are considered next, with particular focus on stochastic impulse control problems that arise when the cost of control includes a fixed cost, common in financial applications. The text proceeds with the development of a fear index based on equity option surfaces, allowing for the measurement of overall fear levels in the market. The problem of American option pricing is considered next, applying simulation methods combined with regression techniques and discussing convergence properties. Changing focus to integral transform methods, a variety of option pricing problems are considered. The COS method is practically applied for the pricing of options under uncertain volatility, a method developed by the authors that relies on the dynamic programming principle and Fourier cosine series expansions. Efficient approximation methods are next developed for the application of the fast Fourier transform for option pricing under multifactor affine models with stochastic volatility and jumps. Following this, fast and accurate pricing techniques are showcased for the pricing of credit derivative contracts with discrete monitoring based on the Wiener-Hopf factorisation. With an energy theme, a recombining pentanomial lattice is developed for the pricing of gas swing contracts under regime switching dynamics. The book concludes with a linear and nonlinear review of the arbitrage-free parity theory for the CDS and bond markets.

Handbooks in Operations Research and Management Science: Financial Engineering

Download Handbooks in Operations Research and Management Science: Financial Engineering PDF Online Free

Author :
Publisher : Elsevier
ISBN 13 : 9780080553252
Total Pages : 1026 pages
Book Rating : 4.5/5 (532 download)

DOWNLOAD NOW!


Book Synopsis Handbooks in Operations Research and Management Science: Financial Engineering by : John R. Birge

Download or read book Handbooks in Operations Research and Management Science: Financial Engineering written by John R. Birge and published by Elsevier. This book was released on 2007-11-16 with total page 1026 pages. Available in PDF, EPUB and Kindle. Book excerpt: The remarkable growth of financial markets over the past decades has been accompanied by an equally remarkable explosion in financial engineering, the interdisciplinary field focusing on applications of mathematical and statistical modeling and computational technology to problems in the financial services industry. The goals of financial engineering research are to develop empirically realistic stochastic models describing dynamics of financial risk variables, such as asset prices, foreign exchange rates, and interest rates, and to develop analytical, computational and statistical methods and tools to implement the models and employ them to design and evaluate financial products and processes to manage risk and to meet financial goals. This handbook describes the latest developments in this rapidly evolving field in the areas of modeling and pricing financial derivatives, building models of interest rates and credit risk, pricing and hedging in incomplete markets, risk management, and portfolio optimization. Leading researchers in each of these areas provide their perspective on the state of the art in terms of analysis, computation, and practical relevance. The authors describe essential results to date, fundamental methods and tools, as well as new views of the existing literature, opportunities, and challenges for future research.

Mathematical Modeling And Computation In Finance: With Exercises And Python And Matlab Computer Codes

Download Mathematical Modeling And Computation In Finance: With Exercises And Python And Matlab Computer Codes PDF Online Free

Author :
Publisher : World Scientific
ISBN 13 : 1786347962
Total Pages : 1310 pages
Book Rating : 4.7/5 (863 download)

DOWNLOAD NOW!


Book Synopsis Mathematical Modeling And Computation In Finance: With Exercises And Python And Matlab Computer Codes by : Cornelis W Oosterlee

Download or read book Mathematical Modeling And Computation In Finance: With Exercises And Python And Matlab Computer Codes written by Cornelis W Oosterlee and published by World Scientific. This book was released on 2019-10-29 with total page 1310 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the interplay of stochastics (applied probability theory) and numerical analysis in the field of quantitative finance. The stochastic models, numerical valuation techniques, computational aspects, financial products, and risk management applications presented will enable readers to progress in the challenging field of computational finance.When the behavior of financial market participants changes, the corresponding stochastic mathematical models describing the prices may also change. Financial regulation may play a role in such changes too. The book thus presents several models for stock prices, interest rates as well as foreign-exchange rates, with increasing complexity across the chapters. As is said in the industry, 'do not fall in love with your favorite model.' The book covers equity models before moving to short-rate and other interest rate models. We cast these models for interest rate into the Heath-Jarrow-Morton framework, show relations between the different models, and explain a few interest rate products and their pricing.The chapters are accompanied by exercises. Students can access solutions to selected exercises, while complete solutions are made available to instructors. The MATLAB and Python computer codes used for most tables and figures in the book are made available for both print and e-book users. This book will be useful for people working in the financial industry, for those aiming to work there one day, and for anyone interested in quantitative finance. The topics that are discussed are relevant for MSc and PhD students, academic researchers, and for quants in the financial industry.

Financial Modelling with Jump Processes

Download Financial Modelling with Jump Processes PDF Online Free

Author :
Publisher : CRC Press
ISBN 13 : 1135437947
Total Pages : 552 pages
Book Rating : 4.1/5 (354 download)

DOWNLOAD NOW!


Book Synopsis Financial Modelling with Jump Processes by : Peter Tankov

Download or read book Financial Modelling with Jump Processes written by Peter Tankov and published by CRC Press. This book was released on 2003-12-30 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: WINNER of a Riskbook.com Best of 2004 Book Award! During the last decade, financial models based on jump processes have acquired increasing popularity in risk management and option pricing. Much has been published on the subject, but the technical nature of most papers makes them difficult for nonspecialists to understand, and the mathematic

Financial Modelling

Download Financial Modelling PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 0470744898
Total Pages : 736 pages
Book Rating : 4.4/5 (77 download)

DOWNLOAD NOW!


Book Synopsis Financial Modelling by : Joerg Kienitz

Download or read book Financial Modelling written by Joerg Kienitz and published by John Wiley & Sons. This book was released on 2013-02-18 with total page 736 pages. Available in PDF, EPUB and Kindle. Book excerpt: Financial modelling Theory, Implementation and Practice with MATLAB Source Jörg Kienitz and Daniel Wetterau Financial Modelling - Theory, Implementation and Practice with MATLAB Source is a unique combination of quantitative techniques, the application to financial problems and programming using Matlab. The book enables the reader to model, design and implement a wide range of financial models for derivatives pricing and asset allocation, providing practitioners with complete financial modelling workflow, from model choice, deriving prices and Greeks using (semi-) analytic and simulation techniques, and calibration even for exotic options. The book is split into three parts. The first part considers financial markets in general and looks at the complex models needed to handle observed structures, reviewing models based on diffusions including stochastic-local volatility models and (pure) jump processes. It shows the possible risk-neutral densities, implied volatility surfaces, option pricing and typical paths for a variety of models including SABR, Heston, Bates, Bates-Hull-White, Displaced-Heston, or stochastic volatility versions of Variance Gamma, respectively Normal Inverse Gaussian models and finally, multi-dimensional models. The stochastic-local-volatility Libor market model with time-dependent parameters is considered and as an application how to price and risk-manage CMS spread products is demonstrated. The second part of the book deals with numerical methods which enables the reader to use the models of the first part for pricing and risk management, covering methods based on direct integration and Fourier transforms, and detailing the implementation of the COS, CONV, Carr-Madan method or Fourier-Space-Time Stepping. This is applied to pricing of European, Bermudan and exotic options as well as the calculation of the Greeks. The Monte Carlo simulation technique is outlined and bridge sampling is discussed in a Gaussian setting and for Lévy processes. Computation of Greeks is covered using likelihood ratio methods and adjoint techniques. A chapter on state-of-the-art optimization algorithms rounds up the toolkit for applying advanced mathematical models to financial problems and the last chapter in this section of the book also serves as an introduction to model risk. The third part is devoted to the usage of Matlab, introducing the software package by describing the basic functions applied for financial engineering. The programming is approached from an object-oriented perspective with examples to propose a framework for calibration, hedging and the adjoint method for calculating Greeks in a Libor market model. Source code used for producing the results and analysing the models is provided on the author's dedicated website, http://www.mathworks.de/matlabcentral/fileexchange/authors/246981.

Applications of Fourier Transform to Smile Modeling

Download Applications of Fourier Transform to Smile Modeling PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 3642018084
Total Pages : 338 pages
Book Rating : 4.6/5 (42 download)

DOWNLOAD NOW!


Book Synopsis Applications of Fourier Transform to Smile Modeling by : Jianwei Zhu

Download or read book Applications of Fourier Transform to Smile Modeling written by Jianwei Zhu and published by Springer Science & Business Media. This book was released on 2009-10-03 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses the applications of Fourier transform to smile modeling. Smile effect is used generically by ?nancial engineers and risk managers to refer to the inconsistences of quoted implied volatilities in ?nancial markets, or more mat- matically, to the leptokurtic distributions of ?nancial assets and indices. Therefore, a sound modeling of smile effect is the central challenge in quantitative ?nance. Since more than one decade, Fourier transform has triggered a technical revolution in option pricing theory. Almost all new developed option pricing models, es- cially in connection with stochastic volatility and random jump, have extensively applied Fourier transform and the corresponding inverse transform to express - tion pricing formulas. The large accommodation of the Fourier transform allows for a very convenient modeling with a general class of stochastic processes and d- tributions. This book is then intended to present a comprehensive treatment of the Fourier transform in the option valuation, covering the most stochastic factors such as stochastic volatilities and interest rates, Poisson and Levy ́ jumps, including some asset classes such as equity, FX and interest rates, and providing numerical ex- ples and prototype programming codes. I hope that readers will bene?t from this book not only by gaining an overview of the advanced theory and the vast large l- erature on these topics, but also by gaining a ?rst-hand feedback from the practice on the applications and implementations of the theory.

Handbook of the Economics of Finance

Download Handbook of the Economics of Finance PDF Online Free

Author :
Publisher : Elsevier
ISBN 13 : 9780444513632
Total Pages : 698 pages
Book Rating : 4.5/5 (136 download)

DOWNLOAD NOW!


Book Synopsis Handbook of the Economics of Finance by : G. Constantinides

Download or read book Handbook of the Economics of Finance written by G. Constantinides and published by Elsevier. This book was released on 2003-11-04 with total page 698 pages. Available in PDF, EPUB and Kindle. Book excerpt: Arbitrage, State Prices and Portfolio Theory / Philip h. Dybvig and Stephen a. Ross / - Intertemporal Asset Pricing Theory / Darrell Duffle / - Tests of Multifactor Pricing Models, Volatility Bounds and Portfolio Performance / Wayne E. Ferson / - Consumption-Based Asset Pricing / John y Campbell / - The Equity Premium in Retrospect / Rainish Mehra and Edward c. Prescott / - Anomalies and Market Efficiency / William Schwert / - Are Financial Assets Priced Locally or Globally? / G. Andrew Karolyi and Rene M. Stuli / - Microstructure and Asset Pricing / David Easley and Maureen O'hara / - A Survey of Behavioral Finance / Nicholas Barberis and Richard Thaler / - Derivatives / Robert E. Whaley / - Fixed-Income Pricing / Qiang Dai and Kenneth J. Singleton.

Advances in Mathematical Finance

Download Advances in Mathematical Finance PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 0817645454
Total Pages : 345 pages
Book Rating : 4.8/5 (176 download)

DOWNLOAD NOW!


Book Synopsis Advances in Mathematical Finance by : Michael C. Fu

Download or read book Advances in Mathematical Finance written by Michael C. Fu and published by Springer Science & Business Media. This book was released on 2007-06-22 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: This self-contained volume brings together a collection of chapters by some of the most distinguished researchers and practitioners in the field of mathematical finance and financial engineering. Presenting state-of-the-art developments in theory and practice, the book has real-world applications to fixed income models, credit risk models, CDO pricing, tax rebates, tax arbitrage, and tax equilibrium. It is a valuable resource for graduate students, researchers, and practitioners in mathematical finance and financial engineering.

Affine Diffusions and Related Processes: Simulation, Theory and Applications

Download Affine Diffusions and Related Processes: Simulation, Theory and Applications PDF Online Free

Author :
Publisher : Springer
ISBN 13 : 3319052217
Total Pages : 264 pages
Book Rating : 4.3/5 (19 download)

DOWNLOAD NOW!


Book Synopsis Affine Diffusions and Related Processes: Simulation, Theory and Applications by : Aurélien Alfonsi

Download or read book Affine Diffusions and Related Processes: Simulation, Theory and Applications written by Aurélien Alfonsi and published by Springer. This book was released on 2015-04-30 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives an overview of affine diffusions, from Ornstein-Uhlenbeck processes to Wishart processes and it considers some related diffusions such as Wright-Fisher processes. It focuses on different simulation schemes for these processes, especially second-order schemes for the weak error. It also presents some models, mostly in the field of finance, where these methods are relevant and provides some numerical experiments. The book explains the mathematical background to understand affine diffusions and analyze the accuracy of the schemes.

Inspired by Finance

Download Inspired by Finance PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 3319020692
Total Pages : 553 pages
Book Rating : 4.3/5 (19 download)

DOWNLOAD NOW!


Book Synopsis Inspired by Finance by : Yuri Kabanov

Download or read book Inspired by Finance written by Yuri Kabanov and published by Springer Science & Business Media. This book was released on 2013-10-23 with total page 553 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present volume is dedicated to Marek Musiela, an eminent scholar and practitioner who is perhaps best-known for his important contributions to problems of derivative pricing, theory of term structure of interest rates, theory of defaultable securities and other topics in modern mathematical finance. It includes 25 research papers by 47 authors, established experts and newcomers alike, that cover the whole range of the "hot" topics in the discipline. The contributed articles not only give a clear picture about what is going on in this rapidly developing field of knowledge but provide methods ready for practical implementation. They also open new prospects for further studies in risk management, portfolio optimization and financial engineering.

Natural Computing in Computational Finance

Download Natural Computing in Computational Finance PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 364223335X
Total Pages : 203 pages
Book Rating : 4.6/5 (422 download)

DOWNLOAD NOW!


Book Synopsis Natural Computing in Computational Finance by : Anthony Brabazon

Download or read book Natural Computing in Computational Finance written by Anthony Brabazon and published by Springer Science & Business Media. This book was released on 2011-09-10 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book follows on from Natural Computing in Computational Finance Volumes I, II and III. As in the previous volumes of this series, the book consists of a series of chapters each of which was selected following a rigorous, peer-reviewed, selection process. The chapters illustrate the application of a range of cutting-edge natural computing and agent-based methodologies in computational finance and economics. The applications explored include option model calibration, financial trend reversal detection, enhanced indexation, algorithmic trading, corporate payout determination and agent-based modeling of liquidity costs, and trade strategy adaptation. While describing cutting edge applications, the chapters are written so that they are accessible to a wide audience. Hence, they should be of interest to academics, students and practitioners in the fields of computational finance and economics. which was selected following a rigorous, peer-reviewed, selection process. The chapters illustrate the application of a range of cutting-edge natural computing and agent-based methodologies in computational finance and economics. The applications explored include option model calibration, financial trend reversal detection, enhanced indexation, algorithmic trading, corporate payout determination and agent-based modeling of liquidity costs, and trade strategy adaptation. While describing cutting edge applications, the chapters are written so that they are accessible to a wide audience. Hence, they should be of interest to academics, students and practitioners in the fields of computational finance and economics. The applications explored include option model calibration, financial trend reversal detection, enhanced indexation, algorithmic trading, corporate payout determination and agent-based modeling of liquidity costs, and trade strategy adaptation. While describing cutting edge applications, the chapters are written so that they are accessible to a wide audience. Hence, they should be of interest to academics, students and practitioners in the fields of computational finance and economics. written so that they are accessible to a wide audience. Hence, they should be of interest to academics, students and practitioners in the fields of computational finance and economics.

Analytically Tractable Stochastic Stock Price Models

Download Analytically Tractable Stochastic Stock Price Models PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 3642312144
Total Pages : 371 pages
Book Rating : 4.6/5 (423 download)

DOWNLOAD NOW!


Book Synopsis Analytically Tractable Stochastic Stock Price Models by : Archil Gulisashvili

Download or read book Analytically Tractable Stochastic Stock Price Models written by Archil Gulisashvili and published by Springer Science & Business Media. This book was released on 2012-09-04 with total page 371 pages. Available in PDF, EPUB and Kindle. Book excerpt: Asymptotic analysis of stochastic stock price models is the central topic of the present volume. Special examples of such models are stochastic volatility models, that have been developed as an answer to certain imperfections in a celebrated Black-Scholes model of option pricing. In a stock price model with stochastic volatility, the random behavior of the volatility is described by a stochastic process. For instance, in the Hull-White model the volatility process is a geometric Brownian motion, the Stein-Stein model uses an Ornstein-Uhlenbeck process as the stochastic volatility, and in the Heston model a Cox-Ingersoll-Ross process governs the behavior of the volatility. One of the author's main goals is to provide sharp asymptotic formulas with error estimates for distribution densities of stock prices, option pricing functions, and implied volatilities in various stochastic volatility models. The author also establishes sharp asymptotic formulas for the implied volatility at extreme strikes in general stochastic stock price models. The present volume is addressed to researchers and graduate students working in the area of financial mathematics, analysis, or probability theory. The reader is expected to be familiar with elements of classical analysis, stochastic analysis and probability theory.

The Oxford Handbook of Applied Bayesian Analysis

Download The Oxford Handbook of Applied Bayesian Analysis PDF Online Free

Author :
Publisher : Oxford University Press
ISBN 13 : 0199548900
Total Pages : 924 pages
Book Rating : 4.1/5 (995 download)

DOWNLOAD NOW!


Book Synopsis The Oxford Handbook of Applied Bayesian Analysis by : Anthony O' Hagan

Download or read book The Oxford Handbook of Applied Bayesian Analysis written by Anthony O' Hagan and published by Oxford University Press. This book was released on 2010-03-18 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bayesian Statistics is a dynamic and fast-growing area of statistical research with wide-ranging and far-reaching applications across science, technology, commerce, and industry. This Handbook explores contemporary Bayesian analysis across a variety of techniques and application areas.

Saddlepoint Approximation Methods in Financial Engineering

Download Saddlepoint Approximation Methods in Financial Engineering PDF Online Free

Author :
Publisher : Springer
ISBN 13 : 3319741012
Total Pages : 134 pages
Book Rating : 4.3/5 (197 download)

DOWNLOAD NOW!


Book Synopsis Saddlepoint Approximation Methods in Financial Engineering by : Yue Kuen Kwok

Download or read book Saddlepoint Approximation Methods in Financial Engineering written by Yue Kuen Kwok and published by Springer. This book was released on 2018-02-16 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes recent advances in applying saddlepoint approximation methods to financial engineering. It addresses pricing exotic financial derivatives and calculating risk contributions to Value-at-Risk and Expected Shortfall in credit portfolios under various default correlation models. These standard problems involve the computation of tail probabilities and tail expectations of the corresponding underlying state variables. The text offers in a single source most of the saddlepoint approximation results in financial engineering, with different sets of ready-to-use approximation formulas. Much of this material may otherwise only be found in original research publications. The exposition and style are made rigorous by providing formal proofs of most of the results. Starting with a presentation of the derivation of a variety of saddlepoint approximation formulas in different contexts, this book will help new researchers to learn the fine technicalities of the topic. It will also be valuable to quantitative analysts in financial institutions who strive for effective valuation of prices of exotic financial derivatives and risk positions of portfolios of risky instruments.