G. Charles-Cadogan
posted by Matúš Medo
(21 June 2012)
pdf
ps
other
(116 views, 111 downloads, 0 comments )
We present conditions under which positive alpha exists in the realm of
active portfolio management- in contrast to the controversial result in Jarrow
(2010, pg. 20) which implicates delegated portfolio management by surmising
that positive alphas are illusionary. Specifically, we show that the critical
assumption used in Jarrow (2010, pg. 20), to derive the illusionary alpha
result, is based on a zero set for CAPM with Lebesgue measure zero. So
conclusions based on that assumption may well have probability measure zero of
occurrence as well. Technically, the existence of [Tanaka] local time on a zero
set for CAPM implies existence of positive alphas. In fact, we show that
positive alpha exists under the same scenarios of "perpetual event swap" and
"market systemic event" Jarrow (2010) used to formulate the illusionary
positive alpha result. First, we prove that as long as asset price volatility
is greater than zero, systemic events like market crash will occur in finite
time almost surely. Thus creating an opportunity to hedge against that event.
Second, we find that Jarrow's "false positive alpha" variable constitutes
portfolio manager reward for trading strategy. For instance, we show that
positive alpha exists if portfolio managers develop hedging strategies based on
either (1) an exotic [barrier] option on the underlying asset - with barrier
hitting time motivated by the "market systemic" event, or (2) a swaption
strategy for the implied interest rate risk inherent in Jarrow's triumvirate of
riskless rate of return, factor sensitivity exposure, and constant risk premium
for a perpetual event swap.
The Econophysics Forum
welcomes your comments