The probabilistic price forecasts were
developed by
Bob Myers, Steve Hanson, Jim Hilker, and
Chris Edge
PURPOSE
The futures price for a given commodity
represents the 'market's' best estimate of what the cash price of the commodity
will be at the maturity date specified on the futures contract. This does
not mean, however, that the futures price at any point in time prior to
the contract's maturity will be identical to the commodity's cash price
at maturity. Therefore, while using futures markets can help to reduce
uncertainty when pricing commodities to be delivered at a future date,
there is still some risk involved in using futures prices to forecast cash
prices. The purpose of this web site is to provide individuals with a means
by which they may gain some understanding of the uncertainty involved with
using futures prices to forecast cash prices.
PROBABILISTIC PRICE FORECASTS
It is useful to view a commodity's cash price at the maturity of a futures contract as being random. It is random in the sense that until the maturity date of the futures contract arrives, we are uncertain as to what the corresponding cash price will actually be. Therefore, using commodity futures prices to forecast a commodity's cash price at contract maturity involves some uncertainty. To help measure this uncertainty we can use options written on futures contracts to assign probabilities to ranges of potential prices. In other words, we can provide estimates of the likelihood that the cash price at the option's expiration will take on a value in some specified range of prices.
While the futures price provides a point
forecast of the cash price at contract maturity, it says nothing about
the potential range of prices within which the cash price may fall. Options
prices, on the other hand, reveal information regarding the volatility
of the cash prices at contract maturity (Technically, options written on
futures expire prior to the futures contract maturing, but we ignore this
complication here). Together futures prices and options prices can be used
to determine the underlying probability distribution associated with the
commodity's cash price at the maturity of the futures contract. The graphs
found at this web site were generated using the information contained in
futures and options prices. They are referred to as probabilistic price
forecasts. These graphs indicate the probability of a commodity's cash
price at the option's expiration being within some specified range of prices.
USING THE PROBABILISTIC PRICE FORECASTS
Before explaining how to use the probabilistic
price forecasts found on this web site, there are a few concepts that need
to be explained. Take a look at the graph below.

This is an example of a probabilistic price forecast. On the horizontal axis are potential cash prices (at the futures contract's maturity) for the commodity contract specified at the top of the graph. For example, this graph refers to the wheat futures contract that reaches maturity in May 1999. On the left-hand side of the graph are the probabilities. The curve is called the cumulative distribution function and it matches various prices (or more correctly, ranges of prices) on the horizontal axis with the probabilities on the left-hand side.
Here we explain how to use the graphs.
To do this we will provide the reader with a statistical 'rule' and then
apply the rule in an example to show how it is used in practice. We will
refer to the commodity's actual cash price at the maturity of the futures
contract as x. This is not a known price, it simply represents some possible
value the cash price could take on at contract maturity. Let the letters
a and b represent two specific prices on the horizontal axis. The user
of the graph, based on their particular needs, chooses these prices.
RULE 1:
For any
given cash price a, the probability that the actual cash price at the maturity
of the futures contract, x, is
less than
or equal to a is represented by F(a), where F(a) is the point on the curve
corresponding to some
price a
on the horizontal axis and represents some probability on the left-hand
side. In statistical notation this
is represented
by
Pr(x < or = a) = F(a)
where Pr
stands for the probability of whatever is inside the parentheses. In this
situation it is the probability
that the
cash price at the maturity of the futures contract, x, is less than or
equal to the chosen price a.
We can use the above graph to provide an
example of this concept. It is a good idea to print the graph to facilitate
using it in the examples. To print the graph (and the entire text on how
to use the graphs) simply use your mouse to left-click on the print button
found on the toolbar at the top of your web browser.
EXAMPLE 1:
Suppose
we want to find the probability that the actual cash price at the maturity
of the futures contract will be
less than
or equal to $2.50 (this is a). Using RULE 1 we write
Pr(x < or = a) = F(a).
Now, plugging in the 2.50 for a we have
Pr(x < or = 2.50) = F(2.50) = 0.34 or 34%.
We see that
the probability is 34% that the cash price at the maturity of the futures
contract will be less than or
equal to
$2.50.
To see how this probability was found using
the graph, draw a line from the $2.50 point on the horizontal axis up to
the curve and make a dot on the curve at this point. Next, draw a line
from the dot on the curve to the left-hand side of the graph. The
corresponding number on the left-hand side of the graph then tells us what
the probability of the actual cash price, x, being less than or equal to
$2.50 is.
RULE 2:
For any
given cash price a the probability of the actual cash price at the maturity
of the futures contract, x,
being greater
than a is represented by 1 - F(a). In statistical notation this is
Pr(x > a)
= 1 - F(a).
Again, the above graph provides a convenient
example of how to use this rule.
EXAMPLE 2:
Suppose
we want to find the probability that the actual cash price at the futures
contract's maturity is greater
than $2.50.
Using RULE 2 we have
Pr(x > a) = 1 - F(a).
Plugging in 2.50 for a we get
Pr(x > 2.50) = 1 - F(2.50) = 1 - 0.34 = 0.66 or 66%.
We see that
the probability is 66% that the cash price at the futures contract's maturity
will exceed $2.50.
Here we drew a line from the 2.50 mark
on the horizontal axis to the curve and then over to the left-hand side
of the graph. However, unlike EXAMPLE 1, since we are interested
in finding the probability of the actual cash price at the futures contract's
expiration, x, being greater than $2.50 we need to subtract the probability
on the left-hand side from one.
RULE 3:
For any
given cash prices a and b, such that a < b, the probability that the
actual cash price at the futures
contract's
maturity, x, is between a and b is represented by F(b) - F(a). In statistical
notation this is
represented
by
Pr(a < x < or = b) = F(b) - F(a).
Notice that
the higher price, b in this example, comes first in the subtraction problem.
The way this would actually be carried
out in practice is to find the probability that the actual cash price,
x, is less than or equal to a [Pr(x < or = a) = F(a)] and subtract it
from the probability that the actual cash price, x, is less than or equal
to b [Pr(x < or = b) = F(b)]. Both of these probabilities are found
exactly as shown in EXAMPLE 1. Once again, we can use the above graph to
provide an example of this concept.
EXAMPLE 3:
Suppose
we are interested in finding the probability that the cash price at the
futures contract's maturity will
be between
$2.50 and $2.70 (these are a and b respectively). Using RULE 3 we have
Pr(a < x < or = b) = F(b) - F(a).
Next we use RULE 1 to find F(b) and F(a)
Pr(x < or = b) - Pr(x < or = a) = F(b) - F(a).
Plugging in 2.50 for a and 2.70 for b we get
Pr(x < or = 2.70) - Pr(x < or = 2.50) = F(2.70) - F(2.50) = 0.85 - 0.34 = 0.51 or 51%.
We see that
the probability is 51% that the actual cash price at the futures contract's
maturity will be between
$2.50 and
$2.70.
What we learned form this example is that if someone was interested in finding the probability that the cash price, x, was between $2.50 and $2.70 they would subtract the probability of the actual cash price, x, being less than or equal to $2.50 [F(2.50)] from the probability of the actual cash price being less than or equal to $2.70 [F(2.70)]. Again, these probabilities are found using RULE 1 as illustrated in EXAMPLE 1.
Now you have the tools necessary to use
the probabilistic price forecasts found on this web site.
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