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One of my clients is a bunker fuel distributor. They
source various grades of oil, blend them into bunker fuel, and sell it
to ships in ports around the world. Each port is its own market. In some
ports, my client is a two-bit player. In others, it is the market maker.
In those ports, they largely set the price of bunker. Unlike a price
taker, who tends to pay more when supply is short, they can influence
prices to benefit themselves. When they have excess supply in a port,
they can sometimes increase the price to make a profit. When their
supply is low, and competitors are selling more, they try to drive the
price down.
What does this mean for value-at-risk (VaR)? Risk
is exposure to uncertainty. VaR quantifies market risk by treating
volatility as a proxy for uncertainty. For your typical price taker,
this is fine, but not for a market maker. If market makers drive prices
up or down to benefit themselves, there is nothing uncertain about the
resulting volatility—at least not for them. The volatility isn’t a risk
for them so much as a way of doing business. It is kind of pointless
calculating VaR for them based on the market volatility they created!
When we "measure" risk, we aren't really measuring
risk. We are measuring some proxy for risk, such as value-at-risk,
portfolio volatility or fatalities per passenger-mile. Sometimes a proxy
used by others isn't so useful for us. This is the situation my client
is in.
Market makers face their own set of risks related
to liquidity and informational asymmetry. These aren't such a problem
for my bunker fuel client, since theirs is not a leveraged market. Such
problems are more significant for market makers in the capital markets,
where leverage abounds. In the capital markets, every time a market
maker quotes a large transaction for a sophisticated counterparty, she
has to wonder "what does he know that I don't?" The very fact that the
knowledgeable counterparty wants to put on the trade increases the
likelihood that the trade will move against the market maker. VaR
doesn't recognize this either.
If VaR is a poor proxy for trading risks faced by
market makers, why do the Basel Accords embrace VaR as their proxy for
measuring risk in bank's trading books? After all, many market makers
are banks. The answer seems to be that no one has ever devised an
effective proxy for the trading risks of market makers. It is easy to
criticize what exists—people criticize VaR all the time. It is more
difficult to come up with something better. Until we do come up with
something better, I suspect the typical CEO of a market making firm
would prefer a daily VaR report over nothing.
Glyn A. Holton
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