Business

Financial
Institutions
Center
Modeling Liquidity Risk, With
Implications for Traditional
Market Risk Measurement and
Management
by
Anil Bangia
Francis X. Diebold
Til Schuermann
John D. Stroughair
99-06
THE WHARTON FINANCIAL INSTITUTIONS CENTER
The Wharton Financial Institutions Center provides a multi-disciplinary research approach to
the problems and opportunities facing the financial servicesindustry in its search for
competitive excellence. The Center's research focuses on the issues related to managing risk
at the firm level as well as ways to improve productivity and performance.
The Center fosters the development of a community of faculty, visiting scholars and Ph.D.
candidates whose research interests complement and support the mission of the Center. The
Center works closelywith industry executives and practitioners to ensure that its research is
informed by the operating realities and competitive demands facing industry participants as
they pursue competitive excellence.
Copies of the working papers summarized here are available from the Center. If you would
like to learn more about the Center or become a member of our research community, please
let us know of yourinterest.
Anthony M. Santomero
Director
The Working Paper Series is made possible by a generous
grant from the Alfred P. Sloan Foundation
1Anil Bangia is at Oliver, Wyman & Company.
Francis X. Diebold is at the University of Pennsylvania, the Stern School, NYU, and the
Oliver Wyman Institute.
Til Schuermann is at Oliver, Wyman & Company.
John D. Stroughair is at Oliver, Wyman &Company.
We thank Steve Cecchetti and Edward Smith for helpful comments and suggestions. All
remaining errors are ours.
Modeling Liquidity Risk
With Implications for Traditional Market Risk Measurement and Management 1
November 1998
This draft/print: December 21, 1998
Abstract: Market risk management under normal conditions traditionally has focussed on the
distribution of portfolio value changesresulting from moves in the mid-price. Hence the
market risk is really in a “pure” form: risk in an idealized market with no “friction” in
obtaining the fair price. However, many markets possess an additional liquidity component
that arises from a trader not realizing the mid-price when liquidating her position, but rather
the mid-price minus the bid-ask spread. We argue that liquidity risk associatedwith the
uncertainty of the spread, particularly for thinly traded or emerging market securities under
adverse market conditions, is an important part of overall risk and is therefore an important
component to model.
We develop a simple liquidity risk methodology that can be easily and seamlessly integrated
into standard value-at-risk models, and we show that ignoring the liquidity effect canproduce
underestimates of market risk in emerging markets by as much as 25-30%. Furthermore, we
show that the BIS inadvertently is already monitoring liquidity risk, and that by not modeling
it explicitly and therefore capitalizing against it, banks will be experiencing surprisingly many
violations of capital requirements, particularly if their portfolios are concentrated in emerging
markets.
-2-“Portfolios are usually marked to market at the middle of the bid-offer spread,
and many hedge funds used models that incorporated this assumption. In late
August, there was only one realistic value for the portfolio: the bid price.
Amid such massive sell-offs, only the first seller obtains a reasonable price for
its security; the rest loose a fortune by having to pay a liquidity premium
if they wanta sale. …Models should be revised to include bid-offer behaviour.”
Nicholas Dunbar (“Meriwether’s Meltdown,” Risk, October 1998, 32-36)

Вступление
Недавний бепорядок на рынке ценных бумаг привел как экспертов так и непрофессионалов к тому, что они сочли виновным во всем риск потерь, связанных с трудностями в продаже активов. когда рынки истощились, и неопытные и умудренные опытом игроки были...