第十九屆亞太財務經濟會計及管理會議 The Efficient Markets Hypothesis The Demise of...
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第第第第第第第第第第第第第第第第第 The Efficient Markets Hypothesis The Demise of the Demon of Chance? Stephen J. Brown NYU Stern School of Business he 19th Annual Conference on Pacific Basin Finance Economics, Accounting, and Management
第十九屆亞太財務經濟會計及管理會議 The Efficient Markets Hypothesis The Demise of the Demon of Chance? Stephen J. Brown NYU Stern School of Business The 19th Annual
The Efficient Markets Hypothesis The Demise of the Demon of
Chance? Stephen J. Brown NYU Stern School of Business The 19th
Annual Conference on Pacific Basin Finance, Economics, Accounting,
and Management
Slide 2
Major developments over last 40 years Portfolio theory
Slide 3
Major developments over last 40 years Portfolio theory Asset
pricing theory
Slide 4
Major developments over last 40 years Portfolio theory Asset
pricing theory Efficient Markets Hypothesis
Slide 5
Major developments over last 40 years Portfolio theory Asset
pricing theory Efficient Markets Hypothesis Corporate finance
Slide 6
Major developments over last 40 years Portfolio theory Asset
pricing theory Efficient Markets Hypothesis Corporate finance
Derivative Securities, Fixed Income Analysis
Slide 7
Major developments over last 40 years Portfolio theory Asset
pricing theory Efficient Markets Hypothesis Corporate finance
Derivative Securities, Fixed Income Analysis Market
Microstructure
Slide 8
Major developments over last 40 years Portfolio theory Asset
pricing theory Efficient Markets Hypothesis Corporate finance
Derivative Securities, Fixed Income Analysis Market Microstructure
Behavioral Finance
Slide 9
The EMH was responsible for the GFC Neo-liberal policy
prescriptions flow from the core theoretical belief in the
superiority of unregulated markets - particularly unregulated
financial markets. These claims ultimately rest on the
"efficient-markets hypothesis", which, in its strongest form,
claims that financial-market prices, like stock-market prices,
incorporate all available information, and therefore represent the
best possible estimate of asset prices. It follows, therefore, that
if markets are fully efficient and prices fully informed, there is
no reason to believe that asset-price bubbles are probable; and if
these do occur, markets will self-correct; and that there is
therefore no justification for government intervention to stop them
occurring Kevin Rudd The Monthly 42 (February 2009)
Slide 10
The EMH was responsible for the GFC The incredibly inaccurate
efficient market theory was believed in totality by many of our
financial leaders, and believed in part by almost all. It left our
economic and government establishment sitting by confidently, even
as a lethally dangerous combination of asset bubbles, lax controls,
pernicious incentives and wickedly complicated instruments led to
our current plight. Surely, none of this could be happening in a
rational, efficient world, they seemed to be thinking. And the
absolutely worst part of this belief set was that it led to a
chronic underestimation of the dangers of asset bubbles breaking.
Jeremy Grantham (quoted in the New York Times June 5, 2009)
Slide 11
Granthams performance over GFC Sharpe Ratio Alpha (market
benchmark) Alpha (Fama French 3 factor) GMO US Equity Allocation
Fund; Class III Shares-0.284-0.00288 (-0.94)-0.00264 (-0.80) GMO
Tobacco-Free Core Fund; Class III Shares-0.268-0.00215
(-0.71)-0.00261 (-0.81) GMO US Quality Equity Fund; Class VI
Shares-0.245-0.00113 (-0.31)-0.00043 (-0.11) GMO US Quality Equity
Fund; Class V Shares-0.245-0.00112 (-0.30)-0.00041 (-0.10) GMO US
Quality Equity Fund; Class IV Shares-0.246-0.00116 (-0.31)-0.00045
(-0.12) GMO US Quality Equity Fund; Class III Shares-0.247-0.00121
(-0.33)-0.00050 (-0.13) GMO Tax-Managed US Equities Fund; Class III
Shares-0.318-0.00473 (-1.62)-0.00435 (-1.40) GMO US Growth Fund;
Class M Shares-0.276-0.00258 (-0.86)-0.00339 (-1.15) GMO US Core
Equity Fund; Class M Shares-0.301-0.00388 (-1.46)-0.00392 (-1.37)
GMO US Core Equity Fund; Class VI Shares-0.295-0.00353
(-1.32)-0.00355 (-1.23) GMO US Core Equity Fund; Class IV
Shares-0.295-0.00357 (-1.33)-0.00359 (-1.24) GMO US Core Equity
Fund; Class III Shares-0.296-0.00362 (-1.36)-0.00363 (-1.26) GMO US
Intrinsic Value Fund; Class III Shares-0.353-0.00736
(-2.44)-0.00708 (-2.30) GMO US Small/Mid Cap Growth Fund; Class III
Shares-0.306-0.00591 (-1.24)-0.00894 (-2.21) S&P500
Market-0.236 Data from August 07 May 09 from CRSP Mutual Funds
Database
Slide 12
Efficient Markets Hypothesis No traders information gives them
an advantage If information is already incorporated in price
Slide 13
Examples of EMH applications Weak form Efficient Markets
Hypothesis Example: trading rule tests Does active management
outperform passive benchmark? Semi-strong form EMH Example: Event
studies What information releases are material to investors?
Empirical asset pricing Example: Orthogonality condition in GMM Can
we explain cross sectional dispersion in required return?
Slide 14
Efficient Markets Hypothesis Tests of Efficient Markets
Hypothesis Does the market efficiently process information? What is
information? Estimation of parameters Does the market efficiently
price risk? What determines the cross section of expected
returns?
Slide 15
Efficient Markets Hypothesis
Slide 16
Random Walk Hypothesis
Slide 17
Random Walk Hypothesis The series looks like a wandering one,
almost as if once a week the Demon of Chance drew a random number
from a symmetrical population of fixed dispersion and added it to
the current price to determine the next weeks price Kendall
(1953)
Slide 18
Random Walk Hypothesis Serial Correlation tests Variance ratio
tests
Slide 19
Random Walk Hypothesis Serial Correlation tests Variance ratio
tests Momentum Zero investment portfolio
Slide 20
Random Walk Hypothesis Well established statistical properties
Strong assumption of stationarity Time varying conditional
expectations not allowed Neither necessary nor sufficient for
EMH
Slide 21
Trading rule tests of EMH Timmerman (2007) survey Nave models
using past sample means hard to beat Recent financial data is most
relevant Short lived episodes of limited predictability
Predictability is not profitability Necessity: Do not consider all
possible patterns of returns Sufficiency: Cannot profit if all
markets rise and fall together
Slide 22
Examining profitability Appearance of short term
profitability.. at the expense of significant downside risk
(Goetzmann et al. 2008) Benchmark Portfolio Socit Gnrale Jan 2008
Jrme Kerviel Nick Leeson
Slide 23
An important seminal reference
Slide 24
Trading Rules: Cowles 1933 Cowles, A., 1933 Can stock market
forecasters forecast? Econometrica 1 309-325 William Peter
Hamiltons Track Record 1902-1929 Classify editorials as Sell, Hold
or Buy Novel bootstrap in strategy space Return on DJI
Slide 25
Trading rule predicting sign of excess return January 1970 -
December 2005 Factor-augmented AR logit based on prior 120 month
rolling window Trading rule value S&P500 value
Slide 26
Cowles Bootstrap Jan 1970-Dec 2005 Annualized excess fund
return 2.203% Sharpe ratio of fund 0.063 Sharpe ratio of S&P500
0.049 Peseran & Timmermann (1992) p-value 4.83% Cowles
bootstrap p-value 6.32%
Slide 27
Standard Event Study approach 05 10152025 30 t r t1 r t2 r t3 r
t4 u 01 u 11 u 21 u 02 u 12 u 22 u 03 u 13 u 23 u 04 u 14 u 24 u 05
u 15 u 25 EVENT
Slide 28
Fama Fisher Jensen and Roll
Slide 29
FFJR Redux
Slide 30
Bottom line: is EMH useful? For whom is the EMH true?
Uninformed investors with limited capital? Large well informed and
well endowed investors? Does it have practical implications?
Benchmark comparisons for fund investors? What information is
material to investors? Useful measures of risk and investment risk
premia?
Slide 31
The EMH was not responsible for GFC Banks invested in beta,
thinking it was alpha They borrowed to invest in market risk
Significant debt exposure at cusp of crisis Banks failed to predict
the collapse of the market A direct implication of the EMH