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    Modelling and Forecasting StockIndex Volatility

    a comparison between GARCH models and theStochastic Volatility model

    Supervisor:Professor Moisa Altar

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    Table of Contents

    Competing volatility models

    Data description

    Model estimates and forecasting

    performances Concluding remarks

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    The Stylized Facts

    The distribution of financial time series has heaviertails than the normal distribution

    Highly correlated values for the squared returns

    Changes in the returns tend to cluster

    Why model and forecast volatility?

    investment

    security valuation

    risk managementpolicy issues

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    Competing Volatility ModelsARCH/GARCH class of models

    Engle (1982)

    Bollerslev (1986)

    Nelson (1991)

    Glosten, Jaganathan, and Runkle (1993)

    Stochastic Volatility (Variance) model

    Taylor (1986)

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    The GARCH model

    p

    1j jtj

    q

    1i

    2

    iti0t

    ttt

    hrh:.eqiancevar

    hr:.eqmean

    Parameter constraints:

    ensuring variance to be positive

    stationarity condition:

    1j0

    ,1i0

    ,0

    i

    i

    0

    p

    j j

    q

    i i 111

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    Error distribution1. Normal

    The density function:

    Implied kurtosis:

    k=3

    The log-likelihood function:

    t

    t

    t

    thh

    f2

    21exp

    21

    T

    t t

    t

    tNormalh

    hL1

    2

    ln2ln2

    1

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    2. Student-t

    Bollerslev (1987) The density function:

    Implied kurtosis:

    The log-likelihood function:

    2,2

    svar;

    s12

    s21f tt21

    t

    2

    t

    21

    21

    tt

    4,

    4

    23

    k

    T

    t t

    t

    tStudentTL

    1

    2

    2

    2

    21ln1ln

    2

    12ln

    2

    1

    2ln

    2

    1ln

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    3. Generalized Error Distribution (GED)

    Nelson (1991) The density function:

    Implied kurtosis:

    The log-likelihood function:

    3

    21

    ;12

    2

    1exp

    f

    2

    1

    t

    t

    2351

    k

    T

    t

    t

    GEDL

    1

    1ln2ln

    1

    2

    1ln

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    The SV model

    2vtt1tt

    tt

    tttt

    0,N~v,vhh:.eqvolatility

    )h2

    1exp(

    )1,0(N~,r:.eqmean

    Parameter constraints:

    stationarity condition:

    Linearized form:

    1||

    ttt

    tttttt

    vhh

    hhry

    1

    22 27.1)ln()ln(

    2

    ,02

    tt

    VarE

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    Forecast Evaluation Measures Root Mean Square Error (RMSE)

    Mean Absolute Error (MAE)

    Theil-U Statistics

    LINEX loss function

    I

    i

    iiI

    RMSE1

    222 )(1

    I

    i

    iiI

    MAE1

    22

    1

    I

    i ii

    I

    i iiUTheil

    1

    222

    1

    1

    222

    )(

    )(

    I

    i

    iiii aa

    I

    LINEX1

    2222 1)())(exp(1

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    Data Description

    data series: BET-C stock index

    time length:April 17, 1998 - April 21, 2003

    1255 daily returns

    Pt daily closing value of BET-C

    Software: Eviews, Ox

    Descriptive statistics for BET-C return series

    Mean Median Maximum Minimum Std. Dev. Skewness Kurtosis Jarque-Bera Prob.

    0.000102 -0.0000519 0.1038602 -0.0975698 0.0153105 0.106634 9.423705 2160.141 0.000

    1ttt PlnPlnr

    400

    500

    600

    700

    800

    900

    1000

    1100

    1200

    1300

    250 500 750 1000 1250

    BETC

    Daily closing prices of BET-C index

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    TestedHypotheses

    1. Normality

    Histogram of the BET-C returns BET-C return quantile plotted

    against the Normal quantile

    0

    100

    200

    300

    400

    500

    -10 -5 0 5 10

    .

    .

    .

    .

    . . .

    .

    .

    .

    .-4

    -3

    -2

    -1

    0

    1

    2

    3

    4

    -.10 -.05 .00 .05 .10 .15

    R

    NormalQuantile

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    2.Homoscedasticity

    -.12

    -.08

    -.04

    .00

    .04

    .08

    .12

    250 500 750 1000 1250

    RETURN

    .000

    .002

    .004

    .006

    .008

    .010

    .012

    250 500 750 1000 1250

    SQUARED_RETURN

    BET-C return series

    BET-C squared return series

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    3. Stationarity

    Unit root tests for BET-C return series

    ADF Test Statistic -13.53269 1% Critical Value* -3.4384

    5% Critical Value -2.8643

    10% Critical Value -2.5683

    *MacKinnon critical values for rejection of hypothesis of a unit root.

    PP Test Statistic -28.07887 1% Critical Value* -3.4384

    5% Critical Value -2.8643

    10% Critical Value -2.5682

    *MacKinnon critical values for rejection of hypothesis of a unit root.

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    4. Serial independence

    -0.1

    -0.05

    0

    0.05

    0.1

    0.15

    0.2

    0.25

    0.3

    1 4 7 10 13 16 19 22 25 28 31 34

    AC

    PAC

    Autocorrelation coefficients for returns (lags 1 to 36)

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    -0.1

    -0.05

    0

    0.05

    0.1

    0.15

    0.2

    0.25

    0.3

    1 5 913

    17

    21

    25

    29

    33

    AC

    PA

    Autocorrelation coefficients for squared returns (lags 1 to 36)

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    Model estimates and forecastingperformances

    Constant Y(-1) R-squared

    Mean equation with in tercept -0.000355 0.276034 0.076278

    t-statistic

    (probability that the coefficient equals 0)

    -0.768264

    (0.4425)

    9.087175

    (0.000)

    -

    Mean equation without intercept - 0.276769 0.075733

    t-statistic

    (probability that the coefficient equals 0)

    - 9.117758

    (0.000)

    -

    Mean equation specification

    GARCH models

    Methodology:

    - two sets: 1004 observations for model estimation

    252 observations for out-of-sample forecast evaluation

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    Lagnumber

    Correlogram of

    residuals

    Correlogram of

    squared residualsQ-stat Prob Q-stat Prob

    1 0.0085 0.927 103.60 0.000

    5 3.3598 0.645 162.76 0.000

    10 5.7904 0.833 165.21 0.000

    15 8.0496 0.922 167.21 0.0000

    40

    80

    120

    160

    200

    -0.05 0.00 0.05

    Series: Residuals

    Sample 3 1004

    Observations 1002

    Mean -0.000355Median -0.000463

    Maximum 0.093143

    Minimum -0.077582

    Std. Dev. 0.014613

    Skewness -0.022081

    Kurtosis 8.209193

    Jarque-Bera 1132.997

    Probab ilit y 0 .000000

    ARCH Test:

    F-statistic 114.8229 Probability 0.000000

    Obs*R-squared 103.1921 Probability 0.000000

    Residual tests

    White Heteroskedasticity Test:

    F-statistic 63.32189 Probability 0.000000

    Obs*R-squared 112.7329 Probability 0.000000

    ARCH-LM test and White Heteroscedasticity Test

    Autocorrelation tests

    Normality test

    GARCH (1 1) Normal Distribution QML parameter estimates

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    GARCH (1,1)Normal DistributionQML parameter estimates

    Coefficient Std.Error t-value Probability

    AR (1) 0.302055 0.045561 6.630 0.0000

    Constant (V) 0.0000472947 0.141153 3.351 0.0008

    ARCH(Alpha1) 0.320832 0.065118 4.927 0.0000

    GARCH(Beta1) 0.483147 0.102838 4.698 0.0000

    GARCH (1,1)Student-T DistributionQML parameter estimates

    Coefficient Std.Error t-value Probability

    AR(1) 0.280817 0.037364 7.516 0.0000

    Constant(V) 0.0000527251 0.144746 3.643 0.0003

    ARCH(Alpha1) 0.350230 0.067874 5.160 0.0000

    GARCH(Beta1) 0.439533 0.091994 4.778 0.0000

    Student(DF) 4.512539 0.656110 6.878 0.0000

    Diagnostic test based on the news impact curve (EGARCH vs. GARCH)Test Prob

    Sign Bias t-Test 0.41479 0.67830Negative Size Bias t-Test 0.66864 0.50373Positive Size Bias t-Test 0.02906 0.97682Joint Test for the Three Effects 0.47585 0.92416

    Diagnostic test based on the news impact curve (EGARCH vs. GARCH)Test Prob

    Sign Bias t-Test 0.38456 0.70056Negative Size Bias t-Test 0.81038 0.41772Positive Size Bias t-Test 0.21808 0.82736Joint Test for the Three Effects 0.73189 0.86568

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    SVQML parameter estimates

    Coefficient Std. Err or z-Statistic Probability

    C(1) -1.269102 0.450023 -2.820081 0.0048

    C(2) 0.858869 0.050340 17.06149 0.0000

    C(3) -1.486221 0.456019 -3.259119 0.0011

    GARCH (1,1)GED DistributionQML parameter estimates

    Coefficient Std.Er ror t-value Probabil ity

    AR(1) 0.285181 0.057321 4.975 0.0000

    Constant(V) 0.0000496321 0.130000 3.818 0.0001

    ARCH(Alpha1) 0.333678 0.062854 5.309 0.0000GARCH(Beta1) 0.450807 0.091152 4.946 0.0000

    Student(DF) 1.172517 0.081401 14.40 0.0000

    Diagnostic test based on the news impact curve (EGARCH vs. GARCH)Test Prob

    Sign Bias t-Test 0.47340 0.63592Negative Size Bias t-Test 0.82446 0.40968

    Positive Size Bias t-Test 0.14047 0.88829Joint Test for the Three Effects 0.74931 0.86155

    SV modelTo estimate the SV model, the return series was first filtered in order

    to eliminate the first order autocorrelation of the returns

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    In-sample model evaluationa) Residual tests

    Autocorrelation of the residualsLag GARCH(1,1) Nomal GARCH(1,1) Student-T GARCH(1,1) GED SV

    Q-stat. p-value Q-stat. p-value Q-stat. p-value Q-stat. p-value

    1 1.131 0.287 2.289 0.130 2.014 0.156 0.506 0.477

    5 3.286 0.511 4.755 0.313 4.408 0354 2.802 0.591

    10 5.654 0.774 7.046 0.632 6.720 0.667 6.237 0.716

    15 8.679 0.851 10.144 0.752 9.796 0.777 7.571 0.910

    Lag GARCH(1,1) Nomal GARCH(1,1) Student-T GARCH(1,1) GED SV

    Q-stat. p-value Q-stat. p-value Q-stat. p-value Q-stat. p-value

    1 0.127 1 0.204 1 0.186 1 0.589 0.443

    5 3.198 0.362 3.606 0.307 3.499 0.321 2.681 0.613

    10 6.033 0.644 6.235 0.621 6.180 0.627 6.539 0.685

    15 6.782 0.913 6.936 0.905 6.895 0.907 8.824 0.842

    Autocorrelation of the squared residuals

    Kurtosis explanationUnexplained

    kurtosis

    GARCH (1,1) Normal 4.28

    GARCH (1,1) Student-t -7.21

    GARCH (1,1) GED 2.56

    SV -2.05

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    b) In-sample forecast evaluation

    RMSE MAE THEIL-U1

    GARCH 11 Normal 0.0000196062 0.000257336 0.646352

    GARCH 11 T 0.0000195026 0.000256516 0.639539

    GARCH 11 GED 0.0000194814 0.000253146 0.638149

    SV 0.0000186253 0.000231101 0.583293

    LINEX a=-20 a=-10 a= 10 a= 20

    GARCH 11 Normal 7,70895E-09 1,92751E-09 1,92806E-09 7,71335E-09

    GARCH 11 T 7,62777E-09 1,9072E-09 1,90773E-09 7,63198E-09

    GARCH 11 GED 7,61114E-09 1,90305E-09 1,90359E-09 7,61545E-09

    SV 6,95655E-09 1,73942E-09 1,73999E-09 6,96113E-09

    1 Benchmark model - Random Walk

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    Out-of-sample Forecast Evaluation Forecast methodology

    - rolling sample window: 1004 observations- at each step, the n-step ahead forecast is stored- n=1, 5, 10

    Benchmark: realized volatility = squared returns

    .000

    .002

    .004

    .006

    .008

    .010

    .012

    1050 1100 1150 1200 1250

    RR

    Forecast output

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    Forecast output

    0

    0,0005

    0,001

    0,0015

    0,002

    0,0025

    0,003

    0,0035

    0,004

    0,0045

    0,005

    1

    1

    9

    3

    7

    5

    5

    7

    3

    9

    1

    10

    9

    12

    7

    14

    5

    16

    3

    18

    1

    19

    9

    21

    7

    23

    5

    25

    3

    1day

    5days

    10 days

    0

    0,001

    0,002

    0,003

    0,004

    0,005

    0,006

    119

    37

    55

    73

    91

    1

    09

    1

    27

    1

    45

    1

    63

    1

    81

    1

    99

    2

    17

    2

    35

    2

    53

    1day

    5days

    10 days

    0

    0,0005

    0,001

    0,0015

    0,002

    0,0025

    0,003

    0,0035

    0,004

    0,0045

    0,005

    1 20 39 58 77 96115

    134

    153

    172

    191

    210

    229

    248

    1day

    5days

    10 days

    0

    0,0001

    0,0002

    0,0003

    0,0004

    0,0005

    0,0006

    0,0007

    0,0008

    119

    37

    55

    73

    91

    1

    09

    1

    27

    1

    45

    1

    63

    1

    81

    1

    99

    2

    17

    2

    35

    2

    53

    1 day

    5 days

    10 days

    a) GARCH (1,1) Normal c) GARCH (1,1) GED

    b) GARCH (1,1) Student-t d) SV

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    Evaluation Measures

    1-step ahead forecast evaluationRMSE MAE THEIL-U1

    GARCH 11 Normal 0,000035300 0,00022591 0,583721

    GARCH 11 T 0,000035111 0,000204242 0,580597

    GARCH 11 GED 0,000035760 0,000203486 0,591337

    SV 0,000048823 0,000253071 0,807336

    LINEX a=-20 a=-10 a= 10 a= 20

    GARCH 11 Normal 6,30398E-09 1,57614E-09 1,57644E-09 6,30638E-09

    GARCH 11 T 6,23593E-09 1,55923E-09 1,55971E-09 6,2398E-09

    GARCH 11 GED 6,46868E-09 1,61743E-09 1,61795E-09 6,47286E-09

    SV 1,2055E-08 3,01454E-09 3,01612E-09 1,20676E-08

    1 Benchmark model - Random Walk

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    5-step ahead forecast evaluation

    RMSE MAE THEIL-U1

    GARCH 11 Normal 0.0000512767 0.0003042315 0.847915

    GARCH 11 T 0.0000512001 0.0003077174 0.846648GARCH 11 GED 0.0000511668 0.0002983467 0.846097

    SV 0.0000511653 0.0002851430 0.846073

    1 Benchmark model - Random Walk

    LINEX a=-20 a=-10 a= 10 a= 20

    GARCH 11 Normal 1.3297E-08 3.325E-09 3.3268E-09 1.33108E-08

    GARCH 11 T 1.3257E-08 3.315E-09 3.3169E-09 1.32711E-08

    GARCH 11 GED 1.3241E-08 3.311E-09 3.3126E-09 1.32539E-08

    SV 1.3239E-08 3.310E-09 3.3125E-09 1.32534E-08

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    10-step ahead forecast evaluation

    RMSE MAE THEIL-U1

    GARCH 11 Normal 0.0000513675 0.0003060239 0.849416

    GARCH 11 T 0.0000513716 0.0003107481 0.849484

    GARCH 11 GED 0.0000513779 0.000300542 0.849588

    SV 0.0000514735 0.0002870131 0.851169

    LINEX a=-20 a=-10 a= 10 a= 20

    GARCH 11 Normal 1,33445E-08 3,33699E-09 3,33871E-09 1,33583E-08

    GARCH 11 T 1,33467E-08 3,33753E-09 3,33925E-09 1,33604E-08

    GARCH 11 GED 1,33499E-08 3,33834E-09 3,34007E-09 1,33637E-08

    SV 1,33996E-08 3,35077E-09 3,35251E-09 1,34135E-08

    1 Benchmark model - Random Walk

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    Comparison between the statistical featuresof the two sample periods

    In-sample Out-of-sample

    Number of observations 1004 252

    Mean -0.000468 0.002371

    Median -0.000378 0.001137Maximum 0.093332 0.103860

    Minimum -0.097570 -0.065731

    Standard Deviati on 0.015209 0.015531

    Skewness -0.116772 0.925148

    Kurtosis 8.666434 11.94869

    Jarque-Bera 1344.146 880.2563

    Probability 0 0

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    Concluding remarks

    In-sample analysis:

    a) residual tests: all models may be appropriate;

    b) evaluation measures: SV model is the best performer;

    Out-of-sample analysis:

    - for a 1-day forecast horizon GARCH models outperform SV;

    - for the 5-day and 10-day forecast horizon, model

    performances seem to converge;- the best model changes with forecast horizon and with

    forecast evaluation measure;

    - there is no clear winner;

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    Concluding remarks

    Sample construction problems;

    Further research:

    - allowing for switching regimes;

    - allowing for leptokurtotic distributions in the SV

    - a better proxy for realized volatility;

    Bibli h

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    Bibliography

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    Appendix GARCH mean equation

    Dependent Variable: Y

    Method: Least Squares

    Date: 06/23/03 Time: 00:45

    Sample(adjusted): 3 1004

    Included observations: 1002 after adjusting endpoints

    Variable Coefficient Std. Error t-Statistic Prob.

    C -0.000355 0.000462 -0.768264 0.4425

    Y(-1) 0.276034 0.030376 9.087175 0.0000

    R-squared 0.076278 Mean dependent var -0.000487Adjusted R-squared 0.075354 S.D. dependent var 0.015204

    S.E. of regression 0.014620 Akaike info criterion -5.610880

    Sum squared resid 0.213740 Schwarz criterion -5.601080

    Log likelihood 2813.051 F-statistic 82.57675

    Durbin-Watson stat 2.002722 Prob(F-statistic) 0.000000

    1. The AR(1) model with intercept

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    2.The AR(1) model without interceptDependent Variable: Y

    Method: Least Squares

    Date: 06/23/03 Time: 00:46

    Sample(adjusted): 3 1004

    Included observations: 1002 after adjusting endpoints

    Variable Coefficient Std. Error t-Statistic Prob.

    Y(-1) 0.276769 0.030355 9.117758 0.0000

    R-squared 0.075733 Mean dependent var -0.000487

    Adjusted R-squared 0.075733 S.D. dependent var 0.015204

    S.E. of regression 0.014617 Akaike info criterion -5.612286

    Sum squared resid 0.213866 Schwarz criterion -5.607386

    Log likelihood 2812.755 Durbin-Watson stat 2.003016

    Appendix Residual Tests

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    Appendix Residual TestsDate: 06/23/03 Time: 00:48

    Sample: 3 1004

    Included observations: 1002

    Autocorrelation Partial Correlation AC PAC Q-Stat Prob.| | .| | 1 -0.003 -0.003 0.0085 0.927

    .| | .| | 2 -0.011 -0.011 0.1228 0.940

    .| | .| | 3 0.041 0.041 1.8102 0.613

    .| | .| | 4 0.004 0.004 1.8256 0.768

    .| | .| | 5 0.039 0.040 3.3598 0.645

    .| | .| | 6 0.030 0.028 4.2395 0.644

    .| | .| | 7 0.013 0.014 4.4124 0.731

    .| | .| | 8 0.027 0.025 5.1482 0.742

    .| | .| | 9 -0.025 -0.027 5.7834 0.761

    .| | .| | 10 -0.003 -0.005 5.7904 0.833

    .| | .| | 11 0.034 0.029 6.9812 0.801

    .| | .| | 12 0.008 0.008 7.0442 0.855

    .| | .| | 13 0.030 0.029 7.9561 0.846

    .| | .| | 14 -0.007 -0.009 8.0088 0.889

    .| | .| | 15 0.006 0.007 8.0496 0.922

    .| | .| | 16 -0.049 -0.055 10.543 0.837

    .| | .| | 17 0.021 0.020 10.994 0.857

    .| | .| | 18 -0.002 -0.008 10.998 0.894

    .| | .| | 19 0.007 0.009 11.051 0.922

    .| | .| | 20 0.023 0.023 11.599 0.929

    Correlogram of Residuals

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    Date: 06/23/03 Time: 00:49

    Sample: 3 1004

    Included observations: 1002

    Autocorrelation Partial Correlation AC PAC Q-Stat Prob

    .|** | .|** | 1 0.321 0.321 103.60 0.000

    .|* | .|* | 2 0.194 0.101 141.44 0.000

    .|* | .| | 3 0.125 0.041 157.05 0.000

    .|* | .| | 4 0.075 0.010 162.73 0.000

    .| | .| | 5 0.005 -0.043 162.76 0.000

    .| | .| | 6 0.008 0.005 162.82 0.000

    .| | .| | 7 0.042 0.045 164.59 0.000

    .| | .| | 8 0.024 0.003 165.18 0.000

    .| | .| | 9 0.005 -0.012 165.21 0.000

    .| | .| | 10 -0.027 -0.040 165.97 0.000

    .| | .| | 11 -0.004 0.012 165.98 0.000

    .| | .| | 12 -0.009 0.000 166.06 0.000

    .| | .| | 13 -0.028 -0.022 166.84 0.000

    .| | .| | 14 -0.011 0.005 166.96 0.000

    .| | .| | 15 -0.016 -0.012 167.21 0.000

    .| | .| | 16 0.007 0.020 167.26 0.000

    .| | .| | 17 -0.019 -0.020 167.61 0.000

    .| | .| | 18 -0.004 0.005 167.62 0.000

    .| | .| | 19 0.000 0.003 167.62 0.000

    .| | .| | 20 -0.017 -0.019 167.91 0.000

    Correlogram of Squared Residuals

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    ARCH Test:

    F-statistic 114.8229 Probability 0.000000

    Obs*R-squared 103.1921 Probability 0.000000

    Test Equation:

    Dependent Variable: RESID^2

    Method: Least Squares

    Date: 06/23/03 Time: 00:52

    Sample(adjusted): 4 1004

    Included observations: 1001 after adjusting endpoints

    Variable Coefficient Std. Error t-Statistic Prob.

    C 0.000145 1.83E-05 7.903650 0.0000

    RESID^2(-1) 0.321081 0.029964 10.71555 0.0000

    R-squared 0.103089 Mean dependent var 0.000213

    Adjusted R-squared 0.102191 S.D. dependent var 0.000573

    S.E. of regression 0.000543 Akaike info criterion -12.19544Sum squared resid 0.000295 Schwarz criterion -12.18564

    Log likelihood 6105.819 F-statistic 114.8229

    Durbin-Watson stat 2.064939 Prob(F-statistic) 0.000000

    ARCH-LM test

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    White Heteroskedasticity Test:

    F-statistic 63.32189 Probability 0.000000

    Obs*R-squared 112.7329 Probability 0.000000

    Test Equation:

    Dependent Variable: RESID^2

    Method: Least Squares

    Date: 06/23/03 Time: 00:53

    Sample: 3 1004

    Included observations: 1002

    Variable Coefficient Std. Error t-Statistic Prob.

    C 0.000144 1.82E-05 7.933013 0.0000

    Y(-1) -0.000222 0.001125 -0.197479 0.8435

    Y(-1)^2 0.299471 0.026700 11.21598 0.0000

    R-squared 0.112508 Mean dependent var 0.000213

    Adjusted R-squared 0.110731 S.D. dependent var 0.000573

    S.E. of regression 0.000541 Akaike info criterion -12.20501

    Sum squared resid 0.000292 Schwarz criterion -12.19031

    Log likelihood 6117.708 F-statistic 63.32189

    Durbin-Watson stat 2.075790 Prob(F-statistic) 0.000000

    White Heteroskedasticity Test