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Faculty  Working  Paper  91-0151 


330 

B385 

1991:151   COPY  2 


STX 


Dividend  Smoothing,  the  Present  Value  Model, 
and  Negative  Autocorrelations  of  Stock 


Yoon  Dokko 

Department  of  Finance 


Bureau  of  Economic  and  Business  Research 

College  of  Commerce  and  Business  Administration 

University  of  Illinois  at  Urbana-Champaign 


BEBR 


FACULTY  WORKING  PAPER  NO.  91-0151 

College  of  Commerce  and  Business  Administration 

University  of  Illinois  at  Urbana-Champaign 

June  1991 


Dividend  Smoothing,  the  Present  Value  Model, 
and  Negative  Autocorrelations  of  Stock 


Yoon  Dokko,  Assistant  Professor 
Department  of  Finance 


I  would  like  to  thank  Hyuk  Choe  and  Robert  Edelstein  for  their  suggestions  on  this 
paper.   Of  course,  I  am  responsible  for  any  remaining  errors. 


Digitized  by  the  Internet  Archive 

in  2011  with  funding  from 

University  of  Illinois  Urbana-Champaign 


http://www.archive.org/details/dividendsmoothin91151dokk 


Dividend  Smoothing,  the  Present  Value  Model,  and  Negative 
Autocorrelations  of  Stock  Price  Changes 

Abstract 

A  consequence  of  partial  dividend  smoothing  is  that  dividends  revert  (slowly) 
to  their  targets  and  the  stock  price  reverts  to  the  present  value  of  expected 
future  target  dividends.  This  target  reverting  can  cause  stock  price  changes 
to  be  negatively  autocorrelated.  As  dividend  smoothing  increases,  the  neg- 
ative autocorrelation  becomes  less  significant.  The  negative  autocorrelation 
appears  to  be  a  "V"  shaped  function  of  the  length  of  holding  periods.  As 
stock  price  volatility  increases  relative  to  dividend  volatility,  the  negative 
autocorrelation  becomes  more  significant. 


Introduction 

Recent  research  contributions  by  DeBondt  and  Thaler  (1985),  Fama  and 
French  (19S7),  and  Poterba  and  Summers  (1988),  among  others,  find  that 
stock  price  changes  (especially  in  the  long  run)  are  NEGATIVELY  AUTO- 
CORRELATED.  This  finding  contradicts  the  long-standing  hypothesis  in  the 
Finance  literature  that  the  stock  price  is  a  random  walk. 

The  objective  of  this  paper  is  to  analyze  the  observed  negative  autocor- 
relations of  stock  price  changes.  Our  analysis  is  developed  upon  the  present 
value  model  and  motivated  by  the  well-known  fact  that  corporate  managers 
smooth  their  dividend  payments.  The  dividend  depends  in  part  on  a  target 
dividend  and  in  part  on  previous  years'  dividends.1  The  degree  of  dividend 
smoothing  is  inversely  related  to  the  speed  of  dividend  adjustment  to  the 
target.  Hence,  under  partial  dividend  smoothing,  the  dividend  reverts  par- 
tially to  the  target.  Holding  the  discount  rate  constant,  the  stock  price  will 
also  revert  to  the  present  value  of  expected  future  target  dividends.  We 
will  show  below  how  the  negative  autocorrelations  of  stock  price  changes 
are  created  by  the  "target  reverting"  process  of  stock  prices,  and  how  they 
are  affected  by  the  length  of  holding  periods  and  the  degree  of  dividend 
smoothing. 

I.  Analysis 

Following  Lintner  (1956)  and  Fama  and  Babiak  (1968),  we  consider  a  simple 
model  for  dividend  smoothing: 

Dt   =  7(A*-A-i)  +  A-i  (i) 


'See  Lintner  (1956),  Brittain  (1966),  Fama  and  Babiak  (1968),  Marsh  and  Merton 
(1987),  and  Choe  (1990),  among  others. 


where  Dt  is  the  dividend  paid  for  period  r,  D\  is  the  target  dividend  for 
period  t,  and  7(0  <  7  <  1)  is  the  speed  of  the  dividend  adjustment  toward 
the  target.  (1  —  7)  is  the  degree  of  dividend  smoothing.  When  7  =  1, 
the  dividend  immediately  reverts  to  the  target  level  and  is  not  smoothed. 
If  7  =  0,  the  dividend  will  never  revert  to  the  target  and  is  completely 
smoothed. 

The  present  value  model  is 

where  Pt  is  the  stock  price  at  the  beginning  of  period  t  +  1  (or  at  time  t), 
Dt+i  is  the  dividend  paid  during  period  t  + 1  (or  from  time  t  +  i '■  —  1  through 
time  r+t),  k  is  the  discount  rate,  which  is  assumed  to  be  constant,  and  Et  is 
the  investor's  expectations  operator  conditional  upon  information  available 
at  time  r. 

Since  equation  (2)  means  that  EtPt+i  =  (1  +  k)Pt  —  EtDt+\,  from  equa- 
tion (1)  we  have 

EtPt+l   =   (i  +  *)Pt-7£tAVi-(i-7)A.  (3) 

Rational  investors  recognize  corporate  dividend  smoothing  and  incorporate 
the  dividend  smoothing  behavior  (equation  1)  into  the  present  value  model 
(equation  2).  This  generates 

We  define  P*  as  the  present  value  of  expected  future  target  dividends  (here- 
after referred  to  as  the  target  price);  P;  =  ££1  j^jfi.  Solving  for  (l-y)Dt 
in  equation  (4)  yields 

(1-7)A    =    (7  +  W-7(l  +  W.  (5) 


In  equation  (3),  we  substitute  the  right  hand  side  of  equation  (5)  for  (1  — 
y)Dt  and  then  substitute  £t(Pt*+1  +  A*+i)  for  C1  +  k)Pt-  Tnis  ^elds 

EtPt+1    =    7£tp;+1  +  (i-7)pt.  (6) 

Equation  (6)  shows  that  the  speed  of  the  stock  price  adjustment  toward 
the  target  price  is  the  same  as  that  of  the  dividend  adjustment. 

Since  Pt+i  =  EtPt+i  H-fy+i,  where  rjt+i  is  assumed  to  be  a  rational  stock 
price  forecast  error  such  that  cov( rjt1rjt+i)  —  0  for  all  i  ^  0,  from  equation 
(6)  we  have  (time  subscripts  are  reduced  by  1) 

Pt    =    7^-iP;  +  (1  -  7)Pt-i  +  %•  (7) 

If  dividends  are  completely  smoothed  (i.e.,  A  =  1  or  7  =  0),  the  stock  price 
is  a  random  walk  and  cov(Pt+2T  —  Pt+n  Pt+r  —  Pt)  =  0  for  all  r  >  1. 

Let  r  be  the  length  of  holding  periods,  and  A  =  1  —  7  (A  measures  the 
degree  of  dividend  smoothing).  The  change  in  stock  prices  over  r  periods 
is 

Pt+r-Pt      =      p-AL)-l{7(^Hr-ll?W-ft-l/T)  +  ^T-*}       (8) 

where  L  is  the  backward  shift  operator. 

We  assume  that  <72(»7t)  =  tf  for  all  t.  To  compute  the  first-order  au- 
tocorrelation of  Pt+T  —  Pt  for  0  <  A  <  1,  we  need  to  assume  a  stochastic 
process  for  D*  (and  thus  for  P(*).  We  consider  two  cases:  (i)  D*  is  a  white 
noise  around  some  mean;  (ii)  Dj  is  a  random  walk. 


A.  Case  1:  when  D\  is  a  white  noise  around  some  mean. 

We  assume  that 

Dmt  =  D  +  et  (9) 

where  D  is  the  mean  of  D*,  and  et  is  a  white  noise.  It  follows  that  P*  = 
D/k,  and  £t+T_1P;+T  -  Et.xP;  =  0  for  all  t. 
Changes  in  stock  prices  over  r  periods  are 

fl+r-A    =    £^Wi-(l-AT)i>Vi,  (10-a) 

j=0  3=0 


and 


pt+2T-p<+T  =  $;:r+i-(i-AT)EAi^-i 

j=0 


where  $1+?+!  denotes  the  terms  with  T7t+2T,  •  •  •  ,tyt+T+1, 
For  0  <  A  <  1,  we  have 


2(1 -A') 


var(Pt+r-P,)    =  „  l*>  (11-a) 


1-A2 
and 


-(i-y)2 

1-A2 


cov(Pt+2T-Pt+T,Pt+T-P()    =    -1 —J-a*  (11-b) 


The  first-order  autocorrelation  of  stock  price  changes  over  r  periods,  /(r,  7), 
is 

/(nA)    =    ^(l-A')-  (12) 


Holding  r  constant  and  for  0  <  A  <  1,  we  find  that 

dJW1  >  °-  <13> 

This  implies  that  increased  dividend  smoothing  reduces  the  magnitude  of 
negative  autocorrelations  of  stock  price  changes.  Fama  and  French  (1987) 
find  that  the  negative  autocorrelations  of  stock  price  changes  for  the  1941- 
1985  time  period  are  less  significant  than  those  for  the  1926-1985  time 
period.  Similarly,  Kim,  Nelson,  and  Startz  (1989)  find  that  negative  au- 
tocorrelations of  stock  price  changes  may  not  exist  during  the  post- World 
War  II  period.  These  findings  could  be  attributed  to  temporal  shifts  in 
dividend  smoothing.  In  fact,  A  during  the  pre-war  period  is  smaller  than 
that  during  the  post-war  period.  In  particular,  after  the  corporate  income 
tax  reform  in  1952,2  the  dividend  appears  to  depend  mostly  on  the  pre- 
vious year's  dividend.  It  is  found,  using  S  &  P  annual  data,  that  A's  are 
about  0.25  to  0.30  and  0.75  to  0.85,  respectively,  for  the  1932-1951  time 
period  and  the  1952-1986  time  period.3  We  may  conjecture  that  increased 
dividend  smoothing  in  recent  years  has  reduced  negative  autocorrelations 
of  stock  price  changes. 

Holding  A  constant  between  0  and  1,  we  find  that 

*%2  <  o.  (u) 

This  result  would  be  consistent  with  Poterba  and  Summers'  finding  that 
as  the  length  of  holding  periods  increases,  the  magnitude  of  negative  auto- 
correlations of  stock  returns  tends  to  increase.  However,  Fama  and  French 


In  1952,  the  statutory  corporate  income  tax  rate  was  raised  from  15  percent  to  52 
percent. 

3 A  similar  result  is  found  in  Fama  and  French  (1988)  and  Choe  (1990). 


(1987)  observe  that  the  negative  autocorrelations  reach  a  maximum  for  3- 
to  5-year  stock  returns  and  then  decrease  toward  zero  as  the  length  of  hold- 
ing periods  increases.  The  negative  sign  of  ^'  '  may  not  be  the  case  for 
allr. 

B.  Case  2:  when  D\  is  a  random  walk. 

We  assume  that 

d;  =  A-i+«  (is) 

where  et  is  a  white  noise.  It  follows  that 

Dt+1-EtDt+1    =    7€t+1  (16) 

and 

p;  =  *»;_,+<*  (n) 

where  ut  =  tt/k.  Equation  (17)  generates 

Et+T-iPf+r  —  Et-\P?    =    P?+T-i—Pt-v 

=    ut  +  u>t+i  -I-  •  •  •  +  w<+T_i .  (18) 

Equation  (8),  the  stock  price  change  over  r  periods,  becomes 

Pt+r-Pt      =      (l-AI)-1{7W.+r-l+-+1Wl  +  I|t+T-^}.  (19) 

For  computing  the  first-order  autocorrelation  of  Pt+T  —  Pti  we  need  to 
understand  the  relationship  between  the  stock  price  forecast  error  (rjt+i)  ^d 
the  dividend  forecast  error  (7£t+i ).  This  is  seen  by  substituting  £^i  ^{i+ffl*' 


6 


for  Pt+1  and  ££,  %%$■  for  Pt  in  the  present  value  model,  Pt+l  =  (l+*)Pt- 
EtDt+i  -f  »7t+i-  It  follows  that 

j=i (I+iy •  (20) 

By  the  law  of  iterative  conditional  expectations,  we  have 

^i+iA+i+i  —  Et  A+i+i   =   a»  ( A+i  —  ^t  A+i)  +  &,«+i 

=    at-7et+1  +  £,t+1  (21) 

where  a,  is  a  regression  coefficient,  and  £,-,*+ 1  is  a  regression  error  such  that 
cov(et+1,f,tf+1)  =  0  for  all  i.  It  is  convenient  to  approximate  a,  as4 

1  -  A,+1 
a.    =    l-T^r.  (22) 

Equation  (20)  becomes 

•         _         "  l  -  aw     "    &w 

**  _  ,+,£(TW  £?uW 

where  c<+1  is  replaced  by  fcu>t+1  (see  equation  17),  and  £t+i  =  HSi  Tr+fcT7' 
Equation  (23)  shows  that  the  stock  price  forecast  error  is  in  principle  de- 
termined by  the  dividend  forecast  error  (wt+i  =  et/k)  and  "other"  forecast 
errors  (&+i)-  Hereafter, 

4Ftom  equation  (1),  we  have  E,+1D,+i+l  -  E,Dt+1+i  =  7(£t+iA"+i+i  -  ^i£f+i+f)  + 
\(Et+lDt4.i  -  EtDt+i)  =  T€l+1(l  +  A  +  ..  +  A1)  =  *=^p(A+i  -  EtDt+1).  For  the  last 
equality,  see  equation  (16). 


Substituting  equation  (23)  into  equation  (19)  generates  (see  Appendix 


A) 


P,+r-P,     =      (l-AI)-W 


T-l 


«^t  +  T   +  7  E  ^t+T-j   +   (7    -   C)Ut   +  6+ 


J  =  l 


T"61 


T-l 


=    E  {(1  -  Xi)  +  «tf }  wk+r-i  +  (1  -  <0(1  -  ^)  E  A^-i 


j=0 


j=0 


T-l 


00 


and 


+  £A'6+r-i-(i-A*)£A'6_.il 

j=0  >=0 


-(i-at)i;a^+t-; 

i=o 

00 


(24-a) 


T(l-c)(l-V)A^AVi 


i=o 


T-l 


OO 


-  (i  -  y)  E  Ai^+T-i  -  (i  -  a')at  e  *&-; 

j=0  j=0 

(24-b) 

where  $!+?+!  denotes  the  terms  with  r/t+2T,"  *,»7«+t+i,&+2t,-  ",6+t+i- 

We  assume  that  cov(u>t+i, (t+J)  =  0  for  all  t  and  ji,  and  var((t)  =  a\  for 
all  t.  Since  &  also  is  a  rational  forecast  error,  cov(ft,  &+,)  =  0  for  all  t  ^  0. 
We  express  o^  as  q<7*,  where  q  is  a  positive  (but  unknown)  constant,  and, 


8 


without  loss  of  generality,  a^  =  1.  For  0  <  A  <  1,  we  have5 

«(*,  -Pt)    =    r  +  2(l-V)fa-_(lrcXc  +  A)}t  (25.a) 

and 

,(1-A^{g-(1-C)(c  +  A)} 
1-A2 

(25-b) 


cov(Pt+2T  -  Pt+T,  Pt+T  -  Pt)    = 


The  first-order  autocorrelation  of  stock  price  changes  over  r  periods  is 

/l  ' '*'    "    t(1-A>)  +  2(1-A'){9-(1-c)(c  +  A)}-  l26; 

This  autocorrelation  can  be  positive  if  {q  —  (1  —  c)(c  +  A)}  is  negative.  This 
happens  for  0  <  q  <  1,  because  — (1  —  c)(c  +  A)  decreases  from  0  to  —1  as 
A  increases  from  0  to  1. 

When  A  =  0  (i.e.,  if  dividends  revert  immediately  to  the  target),  we 
have 

/(t,A  =  0,<?)    =    -^L  <  o.  (27) 

T  +  Zq 

This  illustrates  that  stock  price  forecast  errors  in  the  target  reverting  pro- 
cess cause  stock  price  changes  to  be  negatively  autocorrelated. 

The  sign  of  gj  is  not  clear.  However,  unless  the  dividend  is  extremely 
smoothed,  it  is  likely  that 
a/(r,A,g) 


dr 

and 


<    0  for  r  <  some  r*,  (28-a) 


>    0  for  r  >   some  r*.  (28-b) 


5It  can  be  shown  that  dvar(Pl+T  -  Pt)/dr  >  0,  and  var(/><+i  —  Pt)  is  positive  for  any 
q  >  0.  Hence,  var(Pl+r  —  Pt)  is  positive  for  any  r. 

9 


This  result  implies  that  the  pattern  of  /(r,  A,  q)  is  a  "V"  shape  with  respect 
to  the  length  of  holding  periods.  To  prove  this,  let  x  =  AT(0  <  x  <  A)  so 
that  r  =  gj,  A  =  q  —  (1  —  c)(c  +  A),  which  is  assumed  to  be  positive  for 
the  autocorrelation  to  be  negative,6  and  B  =  ncj-,  which  is  negative.  We 
express  equation  (26)  as 

**  =  jJX^r  (29) 

The  sign  of  g£  is  the  opposite  of  the  sign  of  §£;  as  r  increases  from  1  to  oo, 
x  decreases  from  A  to  0.  The  sign  of  J£  is  the  same  as  the  sign  of  g(x):7 

g(x)    =    2Bx\nx  +  2Ax(l-x)  +  B(l-x).  (30) 

It  follows  that 

g(x  =  0)    =    B  <  0  (31-a) 

g(x  =  \)    =    A(l-A)|(l  +  A)^2+^+2>l}   >  0(?)        (31-b) 

^    =    2J51ni  +  B  +  2^(l-2i) 

=    2(1  -A2)r  +  if^+  2^(1  -2AT)  >  0(?)  (31-c) 

In  A 

Unless  the  dividend  is  extremely  smoothed  (i.e.,  if  A  is  not  close  to  1), 
g(x  =  A)  and  fj  are  likely  to  be  positive.  Then,  f£  <  0  (i.e.,  |f  >  0)  for 
small  r  (i.e.,  large  x),  and  |£  >  0  (i.e.,  |f  <  0)  for  large  r  (i.e.,  small  x). 

Assuming  that  k  =  0.08  and  q  =  1,  Table  1  computes  /(r,  A)  for 
r  =  1,2, •••,10  and  for  A  =  0.25,  0.50,  and  0.75.  These  A  values  would 
correspond  to  those  of  the  pre-war  period,  the  1920s-1980s  period,  and  the 


We  assume  that  q  >  1,  which  implies  that  o\>  at* 

g(x)  —  0  is  the  first-order  condition  for  the  maximum  negative  autocorrelation. 


10 


post-war  period,  respectively.  For  A  =  0.25,  2-year  stock  price  changes 
have  the  largest  negative  autocorrelation.  For  A  =  0.75,  6-year  stock  price 
changes  have  the  largest  negative  autocorrelation.  The  patterns  of  these 
computed  negative  autocorrelations  appear  to  resemble  those  observed  by 
Fama  and  French  (1987). 

Finally,  holding  r  and  A  constant,  we  find  that 

dJ^l3l    <    0.  (32) 

dq 

As  q  increases,  the  magnitude  of  the  negative  autocorrelation  of  stock  price 

changes  increases.  Equation  (23)  shows  that  the  variability  of  stock  prices 

(<j*)  is  determined  by  the  variability  of  dividends  (a* )  and  the  variability  of 

other  variables  (<r|).  Since  <7*  =  qa^  from  equation  (23)  we  have  c2  +  q  = 

oi/<7*.   Hence,  an  increase  in  q  means  that  the  variability  of  stock  prices 

increases  relative  to  the  variability  of  dividends.  To  the  extent  that  firm  size 

is  inversely  related  to  the  magnitude  of  g,  our  result  corroborates  Zarowin's 

(1990)  finding  that  negative  autocorrelations  of  stock  price  changes  are 

observed  mostly  for  small  firms.8 

II.  Summary  and  Concluding  Remarks 

When  the  dividend  paid  reverts  to  a  target  dividend,  the  stock  price  also 
reverts  to  the  present  value  of  expected  future  target  dividends.  Rational 
forecast  errors  of  this  target  reverting  process  can  create  negative  autocor- 
relations of  stock  price  changes.  We  further  find  that  (1)  the  significance  of 
the  negative  autocorrelation  is  inversely  related  to  the  degree  of  dividend 
smoothing;  (2)  the  negative  autocorrelation  appears  to  be  a  "V"  shaped 


'See  also  Chopra,  Lakonishok  and  Ritter  (1991). 

11 


function  of  the  length  of  holding  periods;  (3)  as  the  variability  of  stock 
prices  increases  relative  to  the  variability  of  dividends,  the  negative  auto- 
correlation becomes  more  significant.  Future  empirical  studies  can,  using 
cross-section  data,  test  for  the  characteristics  of  the  behavior  of  stock  price 
changes  which  are  predicted  by  our  present  value  model  analysis. 


12 


References 

Brittain,  John  A.,  Corporate  Dividend  Policy,  Washington,  D.C.:  The  Brook- 
ings Institution,  1966. 

Choe,  Hyuk,  Intertemporal  and  Cross-Sectional  Variation  of  Corporate  Div- 
idend Policy,  Unpublished  Ph.D.  Dissertation,  University  of  Chicago, 
December  1990. 

Chopra,  Navin,  Josef  Lakonishok,  and  Jay  R.  Ritter,  "Performance  Mea- 
surement Methodology  and  the  Question  of  Whether  Stocks  Overreact," 
Working  Paper,  University  of  Illinois,  1991. 

DeBondt,  Warner  F.,  and  Richard  M.  Thaler,  "Does  the  Stock  Market  Over- 
react?" Journal  of  Finance  vol.  40,  no.  3  (July  1985),  pp.  793-805. 

Fama,  Eugene  F.,  and  Harvey  Babiak,  "Dividend  Policy:  An  Empirical 
Analysis,"  Journal  of  American  Statistical  Association  vol.  63,  no.  324 
(December  1968),  pp.  1132-61. 

Fama,  Eugene  F.,  and  Kenneth  R.  French,  "Permanent  and  Temporary 
Components  of  Stock  Prices,"  Journal  of  Political  Economy  vol.  96,  no. 
2  (April  1988),  pp.  246-73. 

Fama,  Eugene  F.,  and  Kenneth  R.  French,  "Dividend  Yields  and  Expected 
Stock  Returns,"  Journal  of  Financial  Economics  vol.  22,  no.  1  (October 
1988),  pp.  3-25. 

Kim,  Myung  Jig,  Charles  R.  Nelson,  and  Richard  Startz,  "Mean  Reversion 
in  Stock  Prices?"  Working  Paper,  University  of  Washington,  1989. 

Lintner,  John,  "Distribution  of  Incomes  among  Dividends,  Retained  Earn- 
ings and  Taxes,"  American  Economic  Review  vol.  46,  no.  2  (May  1956), 
pp.  97-113. 

Marsh,  Terry  A.,  and  Robert  C.  Merton,  "Dividend  Behavior  for  the  Aggre- 
gate Stock  Market,"  Journal  of  Business  vol.  60,  no.  1  (January  1987), 
pp.  1-40. 

Poterba,  James  M.,  and  Lawrence  H.  Summers,  "Mean  Reversion  in  Stock 
Prices,"  Journal  of  Financial  Economics  vol.  22,  no.  1  (October  1988), 
pp.  27-60. 

Zarowin,  Paul,  "Size,  Seasonality,  and  Stock  Market  Overreaction,"  Journal 
of  Financial  and  Quantitative  Analysis  vol.  25,  no.  1  (March  1990),  pp. 
113-25. 


13 


Appndix  A:  Derivation  of  Equations  (24)  and  (25) 
Equation  (24-a):  0  <  A  <  1. 

Pt+r-Pt     =    (1  -  XL)'1  {cut+T  +  lUt+r-i +  '•'  + 1(ut+i  +  (i  -  cfa  +  {t+T  -  Zt} 
The  right  hand  side  of  this  equation  is  rewritten  as 

aJt+T    +cXvt+r-i    +c\2ut+T-2    +••■     +cAT~1u;t+i  +c\Tut         +cXT+lut-i    + 

+7u;t+T_1      +7Ao;<+T_2     +•••    +7AT_2u;H.1      +fXr~1u>t  +7ATu;t_1     + 

+7u;t+T_2     +  •  •  • 

+7<*>t+i  +7^t  +7^2a;t-i     + 

+(7  -  c)u>t    +(7  -  c)Au;t_!     + 


+6+T  +A^+T-l 


This  is  rearranged  as 


+AT-ie 


t+i  +AT6  +AT+16-i    + 

-6  -A6-i    - 


+  (7  +  cA)u;t+T_1 

+  (7  +  7A  +  cA2)wt+T_2 

+  (7  +  7A  +  7A2  +  cA3)wt+T_3 

+  (7  +  7A  +  ...  +  7AT-2  +  cAT"1)u;t+1 

+  (-c  +  7  +  7A  +  ..-  +  7AT-1+cAT)a;t 

+  (-c  +  7  +  7A+.-.  +  7AT"1  +  cAT)Aa;t_i 


T-l 


OO 


+      EA^+r-i-(l-AT)^A^-i 

i=o  i=o 

The  coefficient  of  o;t+T_;,  for  0  <  j  <  r  -  1,  is 

7(l  +  A  +  ...  +  A'-1)  +  cA' 


=     7 


1-A' 
1- A 


+  cA'   =  1  -  X3 +  cXj  (recall  7  =  1  -  A) 


14 


The  coefficient  of  u>t-j,  for  j  =  0, 1,  •  •  • ,  is 

{-e  +  7(l  +  A+-  ...  +  AT-1)  +  cAT}v 

=     {7\^  "  c(l  -  AT)}  X'  =  (1  -  c)(l  -  AT)A' 


Equation  (24-b): 

To  compute  Pt+2-r  —  P*+t,  we  replace  subscript  <  in  equation  (24-a)  with  t+T  and  relegate 
the  terms  with  r]t+2Tj"  •>ty+T+i>6+2T,'-'>&+r4-i  to  #tS+n  wn^cn  are  unnecessary  for 
computing  cov(Pt+2T  -  P<+T,Pt+T  -  Pt). 


Equation  (25- a):  0  <  A  <  1,  oj  as  1,  and  <r|  =  q. 
var(P<+T  -  F«)  = 

E  {(1  -  *')  +  cA>}2  +  (1  -  c)2(l  -  A')2  f)  A2'  +  g  f  g  A2>  +  (1  -  A')2  £  A2' } 
The  first  sum  becomes 


T-l 


=   £{(i-Ai)Hc2A2'+2c(i-Ai)Ai} 


J=0 

I        =     E{1-2(l-c)A^(l-c)2A^} 
>=o 

2(l-c)(l-AT)      (l-c)2(l-A2-) 

1  _  A  "*"  1  -  A2 

Since  £°i0  A2'  =  ^  and  EJ=J  A2>  =  ^  =  Ez*jg+JQ  it  follows  that 
var(P(+T-P,)    =    r.2d-c)(lrA^)  +  (l-c)»(l-^)(l  +  A^ 


1-A 


l-A2 


(1  -  c)2(l  -  A-)2         f(l-A-)(l-hA-)  +  (l-AT)21 

+  — r^ —  +  <7\ r^ / 


15 


2(1  -  c)(l  -  Xr)      (1  -  c)2(l  -  A*)(l  +  V  + 1  -  AT) 

—     " : : r 


+ 


=    r 


=     r  + 


1  -  A  '  1  -  A2 

g(l-AT)(l  +  AT  +  l-AT) 
1-A2 
2(l-c)(l-A*)      2(1  -  c)2(l  -  A*)      2g(l-A*) 

1-A  1-A2  +      1-A2 

2(l-AT){9  +  (l-c)2-(l-c)(l  +  A)} 


1-A2 


This  leads  to  equation  (24-a)  in  the  main  text. 


Equation  (25-b):  cov  =  cov(Pt+2T  -  Pt+T,Pt+T  -  Pt) 


T-l 


cov     =     (l-c)(i_AT)^{l-(l-C)A>}AJ  +  (l-c)2(l-AT)2AT^A2j 


-is 


j=0 

T-l 


i=o 


oo 


T\2\T 


(1-A')£A2'-(1-At)2At£A2' 
j=o  >=o 

n     ,vi     ml1-**     (i-<0(i-ATXi  +  A*n     (i-c)2(i-AT)2A 

J(1-AT)(1-AT)(1  +  AT)-(1-A-)2AT) 

"U ^ J 

(1  -  C)(l  .  \rf         (1_c)2(1_Ar)2(1^AT_Ar) 
1-A  1-A2 

g(l-AT)2(l  +  AT-AT) 
1-A2 
(1  -  c)(l  -  A-)2(l  +  A)  -  (1  -  c)2(l  -  AT)2  -  g(l  -  AT)2 

1-A2 
-(l-AT)2{<Z  +  (l-c)2-(l-c)(l  +  A)} 
1-A2 

This  leads  to  equation  (25-b)  in  the  main  text. 


16 


Table  1 
Computing  Autocorrelations  of  Stock  Price  Changes 

Equation  (26) 


Length  of 

/(r,A. 

q  =  l,fc  = 

:  0.08) 

Holding  Periods 

A  = 

A  = 

A  = 

w 

0.25 

0.50 

0.75 

1 

-0.230 

-0.140 

-0.059 

2 

-0.233* 

-0.182 

-0.095 

3 

-0.202 

-0.186* 

-0.118 

4 

-0.172 

-0.175 

-0.129 

5 

-0.148 

-0.159 

-0.134 

6 

-0.130 

-0.144 

-0.135* 

7 

-0.116 

-0.131 

-0.133 

8 

-0.105 

-0.119 

-0.129 

9 

-0.095 

-0.109 

-0.124 

10 

-0.087 

-0.100 

-0.119 

*  denotes  the  largest  negative  autocorrelation.