. , , , . XX .
30- . XX , . , , . . . . , . . . , , . . : . . , , , , , , . :
, ;
, ;
, .
, , .
. . , , :
1. , Y = C + I , Y = C + S. , , , Y = C(Y) + S(Y). , :
(APC) (APS);
(MPC) (MPS).
: S = S(Y) = Y C(Y). . , , , . , . , , , . .
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2. , , . , . .
3. . . , . , .
4. . XX , , , , , . (P), (w), (w/p), (i) .
. (C0 > 0). , (), . (S < 0).
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. 32.
, , , , :
APC (average propensity to consume): APC = C/Y, 0 < APC< 1;
APS (average propensity to save): APS = S/Y, 0 < APS < 1.
1:
APC + APS = C/Y + S/Y = Y/Y = 1.
, , , () :
MPC (marginal propensity to consume): MPC = ∆C/∆Y, 0 < MPC < 1;
MPS (marginal propensity to save): MPS = ∆S/∆Y, 0 <MPS < 1. : 0 < ∆C/∆Y < 1.
1:
MPC + MPS = ∆C/∆Y + ∆S/∆Y = ∆Y + ∆Y = 1.
, , , .
, :
1. , ;
2. , .
, , , , , ( ) .
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. 33. : ,
0 (AD0 = C); 1 (AD1 = C + I1). () (Y1). , , . . . (AD2 = C + I2),. E2 Y2. , . , . , , Y1. , . . . , . Y0 , Y1. Y0 , . .
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. 34
, : , , , , . . . , , , , . - - .
. (multiplier) Km , . . , . , 30 . XX . . . .
( ) ( ) . .
:
1. : , , .. , ;
2. .
:
C(Y) + I = Y = C(Y) + S(Y),
C(Y) + I ;
C(Y) + S(Y) .
I ():
I = Y C(Y) = S(Y).
:
∂I = 1 C'(Y) ∂Y = S'(Y) ∂Y,
∂ ;
C'(Y) ;
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S'(Y) .
.
:
Km = ∂Y/∂I = 1 / 1 C'(Y) = 1 / S'(Y).
, . . , (+, ) - , .
: Km = 1/1 C'(Y):
1. (Y) C'(Y). S'(Y) . . ;
2. , ;
3. , , , . , . . ;
4. , (0 < MPC<1). , MPC =0.
1. ?
2. . . ?
3. ?
4. ?
5. ?