travail bulles

Rôle de la spéculation, des « bulles » et du
« short selling »
ECON M831
Financement de l’entreprise, Risque et Rôle des Banques
Professeur : Alain de Crombrugghe
Rédacteurs : Justine Devos et Johann Antoine
Master 120 en Sciences Economiques
Orientation Générale - Finalité Spécialisée
ANNEE ACADEMIQUE 2010-2011
Economics School of Louvain/UCL • Place Montesquieu 3 • 1348 Louvain-la-Neuve
Economics School of Louvain/FUNDP • Rempart de la Vierge 8 • 5000 Namur!!

2
Table&des&matières&:&
!" #$%&'()*%+'$,---------------------------------"."/,
0" 12*%+'$,!,3,4'$(252$%6,%78'&+9)26,-------------------""".":,
;" <;,6.8*)=;%+'$-----------------------------.":,
+" >8?+$+%+'$----------------------------.":,
++" >2)@,%A.26,(2,6.8*)=;%+'$------------------".":,
B" <26,B)==26-------------------------------""."C,
+" >8?+$+%+'$----------------------------."C,
++" D;)662,(2,5;&*78,'),B)==2-----------------""."C,
+++" EA.26,(2,B)==26-----------------------"""""."F,
+G" D+6%'&+9)2---------------------------""."H,
*" <26,G2$%26,I,(8*')G2&%--------------------"---."!J,
+" KG;$%;L26,2%,+$*'$G8$+2$%6-----------------."!!,
/" 12*%+'$,0,3,M;&%+2,%2*7$+9)2------------------------."!0,
;" <;,6.8*)=;%+'$----------------------------."!0,
B" <26,B)==26------------------------------""."!:,
*" <26,G2$%26,I,(8*')G2&%-----------------------."!H,
N" 12*%+'$,/,3,O'$%&P=2,2%,&8L)=;%+'$--------------------""."0J,
:" O'$*=)6+'$---------------------------------""."0/,
C" Q+B=+'L&;.7+2--------------------------------"."0N,
,
&
&
&
&
&
&

3
&
&
Introduction&
M')&,*2)@,9)+,'$%,)$,.2),6)+G+,=R;*%);=+%8,(2,*26,(2&$+S&26,;$$826T,9);$(,=26,58(+;6,.;&=2$%,
(2,U,<K,OV#1W,X,$')6,;)&'$6,&25;&9)8,9)2,*2)@Y*+,$R'$%,.=)6,2$,%Z%2,=2,?;52)@,[2)(+,$'+&,(2,
!\0\",W$,2??2%T,(2.)+6,.2)@,*2,(2&$+2&,;,5;=72)&2)6252$%,8%8,&25.=;*8,.;&,=2,=)$(+,$'+&,(2,
0JJH",>;%2,I,=;9)2==2,=2,5'$(2,2$%+2&,625B=;+%,Z%&2,6)&.&+6,(2,=R;$$'$*2,(R)$2,L&;G2,*&+62,
?+$;$*+S&2,('$%,=26,*'$689)2$*26,6'$%,*2==26,9)2,$')6,;G'$6,2$*'&2,%&'.,B+2$,2$,585'+&2",
M')&,(+&2,G&;+T,=2,.&'*266)6,*')G;+%,(2.)+6,)$,*2&%;+$,%25.6,2%,=R8*=;%252$%,(2,=;,B)==2,$R;,
8%8,9)2,=R2??2%,(2,%&'.,.=;+$,(2,*2%%2,B)==2",K),&2L;&(,(26,*&+626,9)2,=R'$,;,*'$$),()&;$%,*26,
9)2=9)26, (8*2$$+26T, '$, .')G;+%, (S6, ='&6, 6R;%%2$(&2, I, )$2, *&+62, 5'$(+;=2, B2;)*')., .=)6,
L&;G2,9)2,=26,.&8*8(2$%26",];=L&8,%')6,*26,6+L$;)@,;662^,;=;&5;$%T,6)&%')%,9);$(,'$,2$,?;+%,
=;,&8%&'6.2*%+G2T,=26,.'=+%+9)26,8*'$'5+9)26,'$%,*'$%+$)8,I,62,?'$(2&,6)&,=26,%78'&+26,9)2,
=R'$,.2)%,9);=+?+2&,(2,$8'=+B8&;=26",O26,%78'&+26,5'$8%;&+6%26,9)+,6'$%,*7S&26,;),%&S6,*8=SB&2,
8*'$'5+6%2, ]+=%'$, 4&+2(5;$T, ')%&2, =2, ?;+%, 9)R2==26, .&+G+=8L+2$%, =;, 5'$$;+2, *'552,
(A$;5+9)2,8*'$'5+9)2T,&2*'55;$(2$%,=;,$'$,+$%2&G2$%+'$,(2,=R_%;%,(;$6,=;,&8L)=;%+'$,(2,
=;, 5;662, 5'$8%;+&2", OR26%, (;$6, *2, *'$%2@%2, 6*+2$%+?+9)2, 9)R;, 8G'=)8, =2, 6A6%S52, ?+$;$*+2&,
+$%2&$;%+'$;=,2%, (2,?;`'$,L8$8&;=2T,=R8*'$'5+2, 5'$(+;=2,(2.)+6,=26, ;$$826,HJ",E')%,*2*+, ;,
('$*,8%8,)$,2$G+&'$$252$%,.&'.+*2,;),(8G2='..252$%,(2,=;,?+$;$*2,9)+,26%,(2G2$)2,(2,.=)6,
2$,.=)6,2$G;7+66;$%2",a')6,2$,6'552,;&&+G86,I,)$,.'+$%T,%2=,9)2,)$2,*7)%2,(R)$2,;5.=2)&,
;662^,+5.'&%;$%,(26,B')&626,.2)%,(2,$'6,[')&6,;G'+&,(26,2??2%6,2$,*;6*;(2,*'$6+(8&;B=26,6)&,
%')%2, $'%&2, 8*'$'5+2", W$, .;&%;$%, (2, =;, *'$6'55;%+'$, (26, 58$;L26, 2$, &;+6'$, (2,
=R+5.'&%;$*2, 9)R'$%, ;*9)+62, =26, G;=2)&6, 5'B+=+S&26, (;$6, =2)&, 8.;&L$2T, [)69)RI,
=R+$G26%+66252$%, 2%, =;, L26%+'$, (26, 2$%&2.&+626, 9)+, 6'$%, (86'&5;+6, 6')5+62, I, =;, G;=2)&,
;*%+'$$;&+;=2",,
<26,%&;$6?'&5;%+'$6,+$%2&$;%+'$;=26,+$()+%26,.;&,=;,?+$;$*2,6'$%,8L;=252$%,(8*+6+G26",K?+$,(2,
5+2)@, .2$62&, *26, %&;$6?'&5;%+'$6T, +=, 26%, .&8?8&;B=2, (2, $2, .=)6, G'+&, =;, ?+$;$*2, *'552, )$,
;*%2)&,$2)%&2,9)+,;)&;+%,.')&,62)=2,?'$*%+'$,(2,*;=*)=2&,2%,(2,&2$(&2,.)B=+9)26,(26,G;=2)&6,
9)+,=)+,.&82@+6%2$%",O2%%2,;..&'*72,26%,62='$,$')6,+$;..&'.&+82",,,

4
M')&, .;&G2$+&, I, )$2, 52+==2)&2, *'5.&872$6+'$T, (2, %')6, *26, 58*;$+6526, ;+$6+, 9)2, =2)&6,
*'$689)2$*26T,$')6,;G'$6,(8*').8,*2,%&;G;+=,2$,.=)6+2)&6,.;&%+26,(;$6,=269)2==26,$')6,$')6,
*'$*2$%&2&'$6,.&+$*+.;=252$%,6)&,=;,6.8*)=;%+'$T,=26,B)==26,2%,=26,G2$%26,I,(8*')G2&%",
<;,.&25+S&2,.;&%+2,G;,%2$%2&,(2,&2%&;*2&,=R7+6%'&+9)2,(26,8G8$252$%6,+5.'&%;$%,%2=6,9)2,=26,
B)==26,2%,=;,6.8*)=;%+'$",<;,(2)@+S52,62&;,.=)6,%2*7$+9)2,*;&,'$,G;,266;A2&,(2,*'5.&2$(&2,
=26,2??2%6, 2%, =26, &P=26, 9)2,*26, %2&526, '$%, 9);$(,'$,.;&=2, (2, *&+62, ?+$;$*+S&2", <;,%&'+6+S52,,
;B'&(2&;,=;,9)26%+'$,(),*'$%&P=2,2%,=;,&8L)=;%+'$,(26,?;*%2)&6,9)+,62='$,$')6,'$%,[')86,)$,
&P=2, 5;[2)&, (;$6, =;, *&+62, 9)2, $')6, ;G'$6, *'$$)2", 4+$;=252$%T, *'552, *2=;, 62, ('+%T, $')6,
%b*72&'$6,(2,?;+&2,)$2,*'$*=)6+'$",,
,
,

5
Section&1&:&Fondements&théoriques.&
,
1. La&spéculation&
, ,
,Définition(:(
,
<;, 6.8*)=;%+'$, 26%, )$2, ;*%+G+%8, *'552&*+;=2, '), ?+$;$*+S&2, 9)+, *'$6+6%2, I, ;*72%2&, (26,
.&'()+%6T, (26, ;*%+?6, +55'B+=+2&6T, (26, *'==2*%+'$6, '), )$, *'$%&;%, (8&+G8, 2%, (R2$, %+&2&, (26,
B8$8?+*26,G+;,=26,?=)*%);%+'$6,(),5;&*78",
1+, =26, .&+@, 8G'=)2$%, (;$6, =;, (+&2*%+'$, 9)2, =R'$, ;G;+%, .&8(+%2T, '$, 2$, &2%+&2, )$, B8$8?+*2",
=$G2&6852$%T,6+, =26, .&+@, 8G'=)2$%,(;$6,=;,(+&2*%+'$,+$G2&62T,'$, '**;6+'$$2, )$2, .2&%2T,*2%%2,
.2&%2,*'$6%+%)2,=2,&+69)2,(2,=;,6.8*)=;%+'$",
c$2,*;%8L'&+2, (R+$6%&)52$%6,?+$;$*+2&6,.=)6,6.8*+?+9)26, *'552,=26,*'$%&;%6,I,%2&52,2%,=26,
.&'()+%6,(8&+G86,.2&52%%2$%,=;,6.8*)=;%+'$,(2,L&;$(6,5'$%;$%6,5'$8%;+&26,;='&6,9)2,=R'$,$2,
(+6.'62, 9)2, (R)$2, .2%+%2, 6'552, (R;&L2$%, ;), (8.;&%", O26, 5Z526, +$6%&)52$%6, 52%%2$%, 2$,
G2$%2,(26,B+2$6,('$%,'$,$2,(+6.'62,.;6,2$*'&2,2%,9)R+=,?;)(&;,(86,='&6,&;*72%2&,;?+$,(26,=26,
?')&$+&",
<;,6.8*)=;%+'$,.2&52%,=;,U,*')G2&%)&2,(2,&+69)2,X,9)+,26%,=R'.8&;%+'$,G+;,=;9)2==2,=26,;L2$%6,
%&;$6?S&2$%, =2)&6, &+69)26, ;), 6.8*)=;%2)&, ;?+$, (2, 62, *')G&+&", W==2, 26%, (R;+==2)&6, %')%,
.;&%+*)=+S&252$%,$8*266;+&2,.')&,=26,2$%&2.&+626,*;&,*2=;,=2)&,.2&52%,(2,6R;66)&2&,*'$%&2,=26,
*'$689)2$*26, (26, G;&+;%+'$6, (2, .&+@T, (2, (2G+626, '), (2, %;)@, (R+$%8&Z%", W$, .=)6, (2, *2=;T, =;,
6.8*)=;%+'$,.2&52%,(2,&8()+&2,=26,(+6%'&6+'$6,9)+,.2)G2$%,6)&L+&,6)&,=2,5;&*78",
#=,2@+6%2,)$2,5)=%+%)(2,(2,6.8*)=;%2)&6,('$%,=26,.&+$*+.;)@,6'$%,=26,'&L;$+6526,?+$;$*+2&6,2%,
=26,B;$9)26",,
&
&
Deux(types(de(spéculation(:(
&
#=, A, ;, (2)@, %A.26, (2, 6.8*)=;%+'$T, =;, 6.8*)=;%+'$, .'6+%+G2, 2%, =;, 6.8*)=;%+'$, $8L;%+G2", <;,
6.8*)=;%+'$,.'6+%+G2,.2&52%,(2,*'$%&+B)2&,I,=R+$G26%+66252$%,(26,2$%&2.&+626,2%,*2=;,.2&52%,