using r for analyzing loans, portfolios and risk: from academic theory to financial practice
DESCRIPTION
Dr. Sanjiv Das has held positions as at Citibank, Harvard University Professor and Program Director at the FDIC’s Center for Financial Research. His research relies heavily on R for analysis and decision-making. In this webinar, Dr. Das will present a mix of some of his more current and topical research that uses R-based models, and some pedagogical applications of R. He will present: * An R-based model for optimizing loan modifications on distressed home loans, and the economics of these modifications. * A goal-based portfolio optimization model for investors who use derivatives. *Using network modeling tools in R to detect systemically risky financial institutions. *Using R for web delivery of financial models and random generation of pedagogical problems. Promising to be entertaining and enlightening, this webinar will emphasize the interplay of mathematical models, economic problems, and R.TRANSCRIPT
Using R in Academic Finance
Sanjiv R. Das Professor, Santa Clara University
Department of Finance h?p://algo.scu.edu/~sanjivdas/
Outline • High‐performance compuGng for Finance • Modeling the opGmal modificaGon of home loans using R
• IdenGfying systemically risky financial insGtuGons using R network models.
• Goal‐based porOolio opGmizaGon with R • Using R to deliver funcGons/models on the web, and for pedagogical purposes.
R works well with Python and C.
h?p://www.rinfinance.com/RinFinance2010/agenda/
h?p://cran.r‐project.org/web/views/Finance.html
Calling C from R: An Example of Tax‐opGmized PorOolio Rebalancing
Calling C from R: An Example of Tax‐opGmized PorOolio Rebalancing
R CMD SHLIB tax.c
MODIFYING HOME LOANS WITH R MODELS
Topic 1
THE PRINCIPAL PRINCIPLE: OpGmal ModificaGon of Distressed Home Loans (Why Lenders should Forgive, not Foresake Mortgages) STRATEGIC LOAN MODIFICATION: An OpGons based response to strategic default (joint work with Ray Meadows)
Game theoreGc problem: Lender determines the loan modificaGon that maximizes value of loan given that the borrower will act strategically in his best interest.
Model
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Home value
HJM
CorrelaGon
“Iso‐Service” Surface
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Loan balance = $300,000 Home value = $250,000 Remaining maturity = 25 years A = $1,933 per month Amax = $20,000 per year
($1,667 per month)
choose
Some R
Values of Iso‐Service Loans
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Default Put Exercise Region
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L=225,000
L=250,000
Cure risk and Re‐default Risk
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The risk of unnecessary relief, i.e., the borrower would not have ulGmately defaulted.
Providing fuGle relief, leading to ulGmate default anyway.
Value of loan accounGng for willingness to pay
A: borrower income available for housing service, with mean μ and std. dev σ.
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h?p://algo.scu.edu/~sanjivdas/
Logit: Explaining Re‐default
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Reduced‐Form Analysis of SAMs
Home values
Normalize iniGal home value to 1. The opGon to default is ITM when (H > L). There is a home value D at which the borrower will default. D is a “default level” or default exercise barrier. D is a funcGon of the lender share θ, we write it as D(L, θ). D increases in L and in θ. Foreclosure recovery as a fracGon of H is ϕ.
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Default Barrier and Lender Share
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Barrier Model IntuiGon
D=L exp[‐γ(1‐θ)]
Region of no default and gains to SAM
Region of default
H0 = 1
Default Payoff=фD
No default Payoff=L
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A Barrier OpGon DecomposiGon Non‐default component
Default component
Shared AppreciaGon component
PDE
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The Closed‐Form SoluGon
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SAM or not?
MANAGING SYSTEMIC RISK BY ANALYZING NETWORKS USING R THE MIDAS PROJECT @IBM
Topic 2
Paper: “Unleashing the Power of Public Data for Financial Risk Measurement, RegulaGon, and Governance” (with Mauricio A. Hernandez, Howard Ho, Georgia Koutrika, Rajasekar Krishnamurthy, Lucian Popa, Ioana R. Stanoi, Shivakumar Vaithyanathan) IBM Almaden)
Midas Financial Insights
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Annual Report
Proxy Statement Insider Transaction
Loan Agreement
Extract Integrate
Related Companies
Loan Exposure
Exposure by subsidiary
…
…
Raw Unstructured Data
Data for Analysis
Raw Unstructured Data
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Systemic Analysis Systemic Analysis • DefiniGon: the measurement and analysis of relaGonships across enGGes
with a view to understanding the impact of these relaGonships on the system as a whole.
• Challenge: requires most or all of the data in the system; therefore, high‐quality informaGon extracGon and integraGon is criGcal.
Systemic Risk • Current approaches: use stock return correlaGons (indirect). [Acharya, et
al 2010; Adrian and Brunnermeier 2009; Billio, Getmansky, Lo 2010; Kritzman, Li, Page, Rigobon 2010]
• Midas: uses semi‐structured archival data from SEC and FDIC to construct a co‐lending network; network analysis is then used to determine which banks pose the greatest risk to the system.
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Co‐lending Network
• DefiniGon: a network based on links between banks that lend together.
• Loans used are not overnight loans. We look at longer‐term lending relaGonships.
• Lending adjacency matrix: • Undirected graph, i.e., symmetric • Total lending impact for each bank:
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Centrality
• Influence relaGons are circular:
• Pre‐mulGply by scalar to get an eigensystem:
• Principal eigenvector of this system gives the “centrality” score for a bank.
• This score is a measure of the systemic risk of a bank.
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Data
• Five years: 2005—2009. • Loans between FIs only. • Filings made with the SEC. • No overnight loans. • Example: 364‐day bridge loans, longer‐term credit arrangement,
Libor notes, etc. • Remove all edge weights < 2 to remove banks that are minimally
acGve. Remove all nodes with no edges. (This is a choice for the regulator.)
2005
CiGgroup Inc.
J.P. Morgan Chase
Bank of America Corp.
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2006 2007
2008 2009
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Network Fragility • DefiniGon: how quickly will the failure of any one bank
trigger failures across the network? • Metric: expected degree of neighboring nodes
averaged across all nodes.
• Neighborhoods are expected to “expand” when • Metric: diameter of the network.
R ! 2
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Top 25 banks by systemic risk
PORTFOLIO OPTIMIZATION USING R
Topic 3
The research papers for this work are on my web page – just google it. h?p://algo.scu.edu/~sanjivdas/research.htm/ 1. Das, Markowitz, Scheid, and Statman (JFQA 2010), “PorOolio OpGmizaGon with
Mental Accounts” 2. Das & Statman (2008), “Beyond Mean‐Variance: PorOolio with
Structured Products and non‐Gaussian returns.”
Standard OpGmizaGon Problem
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Mean Covariance matrix Risk aversion
Portfolio weights
SOLUTION:
See D, Markowitz, Scheid, Statman (JFQA 2010)
SoluGon Math
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Final soluGon
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Example: ConstrucGon of PorOolios: Available securiGes
Expected returns Standard deviations
Bond 5% 5%
Low-risk stock 10% 20%
High-risk stock 25% 50%
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The correlation between the two stocks is 0.2. Other correlations are zero.
Investor goals (sub‐porOolios)
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Sub‐porOolios and overall porOolio
The expected return of the overall porOolio is the weighted average of the expected returns of the sub‐porOolios.
The risk of the overall porOolio is not the weighted average of the risk of the sub‐porOolios.
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Mean‐variance efficient fronGer
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Real porOolios versus virtual porOolios
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An alternate problem
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For normal returns
Solve for γ
Risk as probability of losses
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Mean-variance problem: Minimize Risk (variance) subject to minimum level of Expected Return.
Behavioral portfolio theory: Maximize Return subject to a maximum probability of falling below a threshold.
Efficient FronGers in the BPT (Mental Account) World
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Short‐Selling Constraints
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Linear program with non‐linear constraints. This is not a standard quadraGc programming problem (QP) like the Markowitz model.
MVT uses a standard QP: quadra6c objecGve funcGon with linear constraints.
Modified Problem
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Standard QP
Amenable to industrial opGmizers; we use the R system with the quadprog package and minpack.lm library.
Standard QP problem with linear constraints
MV FronGer with Short‐selling
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DeviaGng from Normality with Copulas
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Gaussian Copula
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Extended OpGmizaGon Problem
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SoluGon
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Non‐Linear Products
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U is a set of states over n assets
r(u) is a n-vector of random returns
Compute p[r(u)]
Restatement of the problem
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This is a quadratic optimization with linear constraints. Not a quadratic optimization with non-linear constraints.
Introducing Structured Products
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Can we improve the risk-adjusted returns in a portfolio by using puts and calls?
Derivatives are very risky.
And so ….
Are puts opGmal?
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No, they add very little value to the portfolio.
But …
Puts are needed when the threshold return is high
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For high thresholds the investor cannot get an acceptable portfolio without puts.
Should investors use calls?
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Calls are risky too.
But have attractive and high mean returns!
Calls give be?er porOolios
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Improvement is greater than 60 bps !
Structured Product: The Barrier‐M‐note
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Barrier‐M Note
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“Truncated Straddle”
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Return pick-up greater than 250 bps!
Barrier-M-note
Equity‐Indexed Product
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Conclusion • Investors find it easier to think in terms of mental accounts or sub‐porOolios
when trying to reach their separate financial goals. • Behavioral porOolio theory deals with maximizing return subject to managing
the risk of loss. This problem has a mathemaGcal mapping into mean‐variance opGmizaGon, yet is much more general.
• Even with short‐selling prohibited, the loss from sub‐porOolio opGmizaGon is smaller than the loss from misesGmaGng investor preferences.
• ReporGng performance by sub‐porOolio enables investors to track their goals be?er.
• Goal‐based opGmizaGon enables choosing porOolios even when normality is not assumed.
• Goal‐based opGmizaGon provides a framework for including structured products in investor porOolios.
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The research papers for this work are on my web page – just google it. h?p://algo.scu.edu/~sanjivdas/research.htm/ 1. Das, Markowitz, Scheid, and Statman (JFQA 2010), “PorOolio OpGmizaGon with
Mental Accounts” 2. Das & Statman (2008), “Beyond Mean‐Variance: PorOolio with
Structured Products and non‐Gaussian returns.”
PEDAGOGICAL USES FOR R USING THE WEB
Topic 4
h?p://sanjivdas.wordpress.com/
Use the Rcgi package from David Firth: h?p://www.omegahat.org/CGIwithR/
You need two program files to get everything working. (a) The html file that is the web form for input data. (b) The R file, with special tags for use with the CGIwithR package.
R Code called from CGI
h?p://algo.scu.edu/~sanjivdas/Rcgi/mortgage_calc.html
High-performance computing (parallelR)
Calling C from R
Lattice dynamic optimization
Network modeling
Optimization
High-dimensional distributions with copulas
Web functions
Q?