|
Interest rate risk
is risk to the earnings or
market value of a portfolio due to
uncertain future interest rates. Discussions of interest rate risk
can be confusing because there are two fundamentally different ways of
approaching the topic. People who are accustomed to one often
have difficulty grasping the other. The two perspectives are:
a
book value perspective, which
perceives risk in terms of its effect on accounting earnings, and
a
market value perspective—sometimes called an economic perspective—which perceives risk in terms of its effect
on the market value of a portfolio.
The first perspective is typical in banking, insurance and
corporate treasuries, where book value accounting prevails. The latter is
typical in a trading or investment management context.
Interest rate risks can be categorized in different ways,
and there is usually some overlap between categories. One approach—that is
well suited for a book-value perspective—is to break interest rate risk
into three components:
term
structure risk,
basis risk,
options risk.
Term structure risk
(also called yield curve risk or
repricing risk) is risk due to changes in
the fixed income
term structure. It arises if interest rates are fixed on liabilities
for periods that differ from those on offsetting assets. One reason may be
maturity mismatches. Suppose an insurance company is earning 6% on an
asset supporting a liability on which it is paying 4%. The asset matures
in two years while the liability matures in ten. In two years, the firm
will have to reinvest the proceeds from the asset. If interest rates fall,
it could end up reinvesting at 3%. For the remaining eight years, it would
earn 3% on the new asset while continuing to pay 4% on the original
liability. Term structure risk also occurs with
floating rate assets or liabilities.
If fixed rate assets are financed with floating rate liabilities, the rate
payable on the liabilities may rise while the rate earned on the assets
remains constant.
In general, any occasion on which interest rates are to be
reset—either due to maturities or floating rate resets—is called a
repricing. The date on which it occurs is
called the repricing date. It is this
terminology that motivates the alternative name "repricing risk" for tem
structure risk.
If a portfolio has assets repricing earlier than
liabilities, it is said to be asset sensitive.
This is because near term changes in earnings are going to be driven by
interest rate resets on those assets. Similarly, if liabilities reprice
earlier, earnings are more exposed to interest rate resets on those
liability, and the portfolio is called
liability sensitive.
For example, a bank that is supporting fixed rate
liabilities with floating rate assets is asset sensitive.
Earnings risk is
posed by the floating rate on the assets. This example is only meaningful
from a book value standpoint—which focuses on earnings risk. From a market
risk standpoint, the floating rate assets pose little risk—floaters have
stable market values. It is the long-dated liabilities that pose market
risk. Their market values fluctuate with changes in long-term interest
rates. From the economic perspective, it would be reasonable to call the
bank "liability sensitive!" Of course, that is not how the terminology is
used. However, our example highlights how fundamentally different the
book-value and market-value perspectives are.
It should be emphasized that this discussion uses the
terms "asset" and ":liability" loosely, and not in any strict accounting
sense. We include among assets and liabilities both
derivatives and other
off-balance sheet instruments that may behave like assets or liabilities.
A pay-fixed interest rate
swap might be considered a combination of a floating rate asset with a
fixed rate liability. On a stand-alone basis, it poses considerable term
structure risk.
Basis risk is
risk due to possible changes in spreads.
In fixed income markets, basis risk arises form changes in the
relationship between interest rates for different market sectors. If a
bank makes loans at prime while financing those loans at
Libor, it is exposed to the risk that
the spread between prime and Libor may narrow. If a portfolio holds
junk bonds hedged with
short Treasury futures, it is
exposed to basis risk due to possible changes in the yield spread of junk
bonds over Treasuries. Basis risk is another name for
spread risk.
As with term structure risk, book-value and market-value
perspectives differ with respect to basis risk. As always, the book value
perspective focuses on risk to earnings. If the spread between interest
earned on assets and interest paid on liabilities narrows, those earnings
will suffer. The economic perspective considers the risk to the
portfolio's market value. If a spread narrows or widens, the market values
of assets and liabilities may be affected differently—and the net market
value of the overall portfolio could suffer.
Options risk, as a component of interest rate risk, is
risk due to fixed income options—options
that have fixed income instruments or interest rates as
underliers. Options
may be stand-alone, such as caps or
swaptions. They may also be
embedded, as with the call feature of
callable bonds or the
prepayment of
mortgage-baked
securities (MBS). In some respects, options risk is just another
component of term structure risk. This argument needs to be explored
differently for the book value and market value perspectives.
From the book value perspective, the distinction between
term structure and options risk has historical roots.
Payoffs of options depends
upon changes in interest rates, which would seem to make options one more
source of term structure risk. However, by shorting embedded options, a
depository institution can enhance short-term earnings at the expense of
long-term earnings. This is what happened during the 1980s, when the MBS
market was just emerging. Dealers found US thrifts and other depository
institutions to be eager buyers of MBSs. Because of their short embedded
prepayment options, the MBSs offered very high
yields—and those high
yields flowed immediately to earnings. Because MBS pricing was far from
transparent, dealers could charge exorbitant prices for the MBS—they
priced them to have yields much higher than
Treasury notes, but not high
enough to fully compensate for the short options. From an economic
standpoint, thrifts incurred a loss every time they purchased an MBS, but
the thrifts didn't see that. Perceiving the world from a purely
book-value/earnings perspective, all they saw was an immediate jump in
earnings. Only later, when interest rates dropped and prepayments on the
MBS surged, did the thrifts realize their mistake. Loses were staggering
and were a primary contributor to the ensuing crisis in the US thrift
industry.
Part of the thrifts' problem was due to being cheated by
the dealers who sold them the MBS at inflated prices. That is a risk
distinct from interest rate risk. It is as old as Wall Street—caveat
emptor. However, another significant issue was the emerging problem that derivatives and new
structures with embedded options made it possible to do an "end-run" around
traditional book value accounting. Increasingly, earnings could be
manipulated for the short-term, with consequences pushed into the future.
Traditional techniques of asset-liability management—which focused on term
structure and basis risk—were ill equipped to address this emerging risk.
Hence, the new risk was given a name—options risk—and managers came under
pressure to supplement old tools with new ones that could assess this new
risk.
The economic perspective on options risk is very
different. From that standpoint, options pose immediate risk in the form
of changes in their market value. While shorting embedded options can
generate income that immediately flows to earnings, it does nothing for
market value—the option premiums are offset by the negative market value
of the newly shorted options. If the options are shorted at fair prices,
the two cancel—and there is no immediate market value impact.
Market risk of fixed income options arises primarily from
two sources:
changes in
underlying interest rates, and
changes in
applicable implied volatilities.
The first of these, from a market value standpoint, is no
different from term structure risk—the portfolio's value rises or falls
with interest rates in a fairly predictable manner. The latter isn't a
form of interest rate risk—it is implied volatility risk. Accordingly,
from an economic perspective, it is more reasonable to identify just two
components of interest rate risk:
term
structure risk, and
basis risk.
where a term structure includes a component of what we
previously called options risk, and the balance of options risk is a new,
non-interest rate risk:
volatility
risk.
There are many techniques for assessing interest rate
risk. Some focus on the earnings impact of interest rate risk. Others
focus on the market value impact. Accordingly, the choice of tools will be
motivated by your perspective.
Investors with a book value perspective tend to address
interest rate risk with the tools of
asset-liability
management—cash matching,
gap analysis, earnings
simulation, earnings at risk and
duration. Those with
an economic perspective use some of these—especially gap analysis and
duration—but they also use tools that focus on economic value—delta,
PV01 and value-at-risk.
Tools such as earnings simulation and earnings-at-risk
quantify risk in terms of its earnings impact, so they are only applicable
from a book-value perspective. Tools like PV01 and value-at-risk quantify
risk in terms of market value impact, so they are only applicable from a
market-value perspective. Gap analysis and duration are interesting
because they can be used with either perspective. Let's look at why.
Gap analysis doesn't consider the consequences of the risk
it assesses, so it doesn't lock the user into one perspective or the
other. It simply identifies
interest rate gaps. The book-value and market-value perspectives may
see differing implications in those gaps, but they both see risk.
Accordingly, gap analysis is useful for both.
Duration is different. Rather than avoid describing the
consequences of the risks it identifies, it offers two alternative
interpretations of those risks. Based on the
Macaulay formula,
duration is the average weighted maturity of a portfolio. From the
book-value perspective, a portfolio that has positive duration is
liability sensitive. One that has negative duration is asset sensitive.
From the economic perspective, duration describes the sensitivity of the
portfolio's market value to parallel shifts in the
spot curve (see the article
Duration and Convexity).
Accordingly, the single notion of duration is perceived in fundamentally
different ways.
As mentioned earlier, there is no particular need from an
economic perspective to consider a separate options risk. Standard tools,
including delta, vega, PV01 and
value-at-risk—if correctly implemented—easily capture the risks of
options. From a book value perspective, traditional tools, including cash
matching and gap analysis, simply cannot incorporate options. This
necessitated a search for new tools. One was earnings simulation. If
implemented to assess risk over a long-enough horizon—in the past, it
often wasn't— it can
easily incorporate the effects of options over time. Another is
option-adjusted duration.
Abandoning the somewhat limited Macaulay formula, investors would use
option pricing models
to accurately calculate duration as a factor sensitivity. To clarify
terminology, from the book value perspective, duration is Macaulay
duration and option-adjusted duration is what, from an economic
perspective, is called duration. Yes, interest rate risk can be confusing.
Blame it on the two competing perspectives.
|
|
 |
|
bond Securitized debt.
asset-liability management Techniques for protecting a firm's solvency in the context of accrual accounting.
basis risk
Risk from exposure to uncertain spreads.
compounding Simple, compound and continuously compound interest.
corporate risk
management Practices that serve to optimize risk taking in a context of
book value accounting.
duration
and convexity Factor sensitivities often used in
asset-liability management.
financial
risk management Practices by which a firm optimizes the
manner in which it takes financial risk.
fixed income
term structure Refers collectively to a spot curve, forward curve,
discount curve, yield curve or any other curve that describes the time value of
money at a particulate point in time.
gap analysis
A technique of asset-liability management used to assess interest rate risk or
liquidity risk.
interest rate spreads An
overview.
market risk Exposure to the uncertain market value of a portfolio.
option-adjusted spread
Yield spread not attributable to embedded options.
reinvestment
risk Risk from uncertainty in the interest rate at which
future cash flows may be invested.
scenario analysis
Formalized "what if" analysis typically performed as a part of asset-liability management
or corporate risk management.
valuation
Article about book value and market value accounting. |
|
|
|
 |
|
Dermine and Bissada (2002)
describe interest rate risk in the context of asset-liability
management. Marrison (2002)
provides more of the economic perspective. Van Deventer, et al (2004)
blends book-value and market-value perspectives in a discussion
that will appeal to more experienced readers.
|
|
|
|
 |
 |
Ads by Contingency Analysis
|
|
|
 |
|
|
|
|
|