10
Thus, the 2-3/8%-8/24 Treasury security is associated
with the lowest basis and the highest IRR as of October
10, 2017. As a general rule, the security with the lowest
basis will likewise exhibit the highest implied repo rate. It is
possible that a security with the lowest basis may not quite
have the highest IRR because of cash ow considerations.
But this statement is generally true. In any event, this
observation conrms the CTD status of the 2-3/8%-8/24 as
of October 10, 2017.
By buying the basis of a Treasury security, or buying
cash and selling futures, one becomes obligated to make
delivery of the Treasury in satisfaction of the maturing
futures contract.
2
Thus, buying the basis of the cheapest-
to-deliver 2-3/8%- 8/24 vs. a futures contract that matures
two or three months hence, may be considered analogous
to other short-term investment alternatives.
E.g., we might compare the IRR = 1.42% associated with
the CTD security to the prevailing 13-week T-bill yield of
1.04%; or to the eective Fed Funds rate of 1.15%; or, to a
3-month ICE LIBOR rate at 1.34%.
In this example, the IRR associated with the CTD security
was essentially equivalent to other short-term investment
opportunities. As a general rule, however, the IRR even for
the CTD security tends to run at a level that is a bit inferior
to the returns associated with comparable short-term
investment alternatives. The IRRs associated with all other
non CTD securities are even lower.
This begs the question – why would anyone ever want to
buy the basis if the returns do not appear to be competitive?
The answer lies in the fact that the basis conveys other
opportunities apart simply from the opportunity to use the
futures contract as a delivery conveyance.
Consider any discrepancy with respect to the CTD to
represent a risk premium of sorts. If one buys the CTD
security and sells futures with the intention of making
delivery, the worst case scenario has the basis converging
fully to zero and the hedger essentially locking in a return
equal to the IRR, in this case 1.42%.
But if market conditions should change such that another
security becomes CTD, this implies that the basis may
advance, or at least fail to completely converge to zero.
As a result, the trader may realize a rate of return that is in
fact greater than the currently calculated IRR.
2 One may, of course, opt to offset the short futures contract prior to the delivery
period and effectively abrogate such obligation.
Basis Optionality
In other words, there is a certain degree of “optionality”
associated with the purchase or sale of the basis. Buying
the basis is analogous to buying an option which, of
course, implies limited risk. Buying the basis implies
limited risk to the extent that, even under the worst of
circumstances, you make delivery of the security which is
eectively equivalent to the possibility that the basis fully
converges to zero.
But “crossovers” or “switch” may occur such that the basis
converges at a slower rate than otherwise anticipated or
actually advances. As a result, this short-term investment
may generate a return which is (at least theoretically)
unbounded on the upside. Limited risk accompanied by
unbounded upside potential is reminiscent of the risk/
reward prole of a long option position, thus the analogy
between a long basis position and a long option.
The best one may hope by selling the basis, or selling
securities and buying futures with the possibility of
eectively replacing the sold security by standing long in
the delivery process, is that the basis fully converges to
zero. This implies limited prot potential.
But in the event of signicant changes in market
conditions, the basis may advance sharply, exposing
the seller of the basis to (theoretically) unbounded risks.
Limited prot potential accompanied by unbounded risk
is reminiscent of the risk/reward prole of a short option
position, thus the analogy between a short basis position
and a short option.
As discussed above, the basis even for the CTD security
tends to be in excess of cost of carry considerations. This is
manifest in the fact that the IRR even for the CTD is typically
a bit below prevailing short-term rates. This premium in the
basis essentially reects the uncertainties associated with
which security may become CTD in the future.
Thus, the basis performs much akin to an option. Like any
other option, the basis will be aected by considerations
including term, volatility and strike price. The relevant
term in this case is the term remaining until the presumed
delivery date vs. the futures contract. Market volatility
aects the probability that a crossover may occur.
Rather than speak of a strike or exercise price, it is
more appropriate to assess the market’s proximity to a
“crossover point” or a price/yield at which one might expect
an alternate security to become CTD.