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Capitolo 6

Capitolo 6. La Domanda del settore privato: consumo e investimento. Fig. 6.01. Variability of GDP Components, 1970-2001. Figure 6.1. Fig. 6.02(a). Indifference curves: Normal case. Consumption tomorrow. 0. Consumption today. Figure 6.2(a). Fig. 6.02(b).

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Capitolo 6

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  1. Capitolo 6 La Domanda del settore privato: consumo e investimento

  2. Fig. 6.01 Variability of GDP Components, 1970-2001 Figure 6.1

  3. Fig. 6.02(a) Indifference curves: Normal case Consumption tomorrow 0 Consumption today Figure 6.2(a)

  4. Fig. 6.02(b) Indifference curves: Zero substitution Consumption tomorrow 0 Consumption today Figure 6.2(b)

  5. Fig. 6.02(c) Indifference curves: Constant substitution Consumption tomorrow 0 Consumption today Figure 6.2(c)

  6. Fig. 6.03 Optimal consumption Begin Figure 6.3

  7. Fig. 6.03 D • Consumption today financed on credit M Y2 (ii) (ii) Consumption loan repayment (including interest) R C2 IC3 IC2 (i) IC1 -(1+r) Y1 C1 B Optimal consumption: borrower Consumption tomorrow 0 Consumption today Figure 6.3(a)

  8. Fig. 6.03 • Saving from this period’s income (ii) Additional consumption next period R C2 (ii) (i) -(1+r) C1 Optimal consumption: lender D Consumption tomorrow Y2 A IC3 IC2 IC1 Y1 B 0 Consumption today Figure 6.3(b)

  9. Fig. 6.04 Ciclo di vita del consumo Figure 6.4

  10. Consumo ottimale

  11. La funzione di utilità sopra scritta si ottiene sostituendo al posto di C1 l’espressione del lucido precedente e trascurando  che è costante

  12. Fig. 6.04 Income Saving Permanentincome Consumption Borrowing Life-cycle consumption Income,Consumption 0 Time Figure 6.4

  13. Fig. 6.05 Variazioni permanenti e temporanee del reddito Figure 6.5

  14. Fig. 6.05 D´ D R´ Y2 A´ A=R Y1 Y1´ B B´ Temporary income change Consumption tomorrow 0 Consumption today Figure 6.5

  15. Fig. 6.05 A´´R´´ Y2´ B´´ Permanent income change D´ D Consumption tomorrow R´ Y2 A´ A=R Y1 Y1´ B B´ 0 Consumption today Figure 6.5

  16. Fig. 6.05 A´´R´´ Y2´ Temporary vs. permanent income change D´ Temporary: R to R´ Permanent: R to R´´ D Consumption tomorrow R´ Y2 A´ A=R Y1 Y1´ B B´ B´´ 0 Consumption today Figure 6.5

  17. Fig. 6.06 Real GDP and retail sales growth:Czech Republic, 1997-2002 Figure 6.6

  18. Fig. 6.07 Real price of crude oil, 1956-2002 Figure 6.7

  19. Fig. 6.08 Current accounts in three countries, 1956-2002 Figure 6.8

  20. Fig. 6.09 Gli effetti di un aumento del tasso di interesse Figure 6.9

  21. Fig. 6.09 D D A R R A B B Recall: borrowers consume to the right of their endowment A, lenders to the left of A. Consumption tomorrow Consumption tomorrow Consumption today Consumption today (a) Student Crusoe(borrower) (b) Professional athlete(lender) Figure 6.9

  22. Fig. 6.09 R´ R´ B´ B´ Effect of an increase in the interest rate: negative income effect for borrowers, positive for lenders D D A Consumptiontomorrow Consumption tomorrow R R A B B Consumption today Consumption today (a) Student Crusoe(borrower) (b) Professional athlete(lender) Figure 6.9

  23. Fig. 6.09 R´ R´ B´ B´ For borrowers: income and substitution effects work in the same direction (to increase saving) D D A Consumption tomorrow Consumption tomorrow R R A B B Consumption today Consumption today (a) Student Crusoe(borrower) (b) Professional athlete(lender) Figure 6.9

  24. Fig. 6.09 R´ R´ B´ B´ For lenders: income and substitution effects work in opposite directions (below income effect wins) D D A Consumption tomorrow Consumption tomorrow R R A B B Consumption today Consumption today (a) Student Crusoe(borrower) (b) Professional athlete(lender) Figure 6.9

  25. Fig. 6.10 Consumption, wealth and disposable income: France, 1980-2002 Fig. 6.10

  26. Fig. 6.11 I vincoli al credito Figure 6.11

  27. Fig. 6.11 C A repay R borrow When the household is not credit constrained... Consumption tomorrow D 0 Consumption today Figure 6.11

  28. Fig. 6.11 B With a credit constraint, the choice set is reduced. C Consumption tomorrow A R D 0 Consumption today Figure 6.11

  29. Funzione del consumo: C = C(, Yd)

  30. Fig. 6.12 GDP, domestic demand and the current account: Poland and East Germany Figure 6.12

  31. Fig. 6.13 Lo stock ottimale di capitale Figure 6.13

  32. Fig. 6.13 R Marginal cost of capital MPK Output Output Optimal capital stock is larger than starting capital stock Capital stock Marginal productivity of capital We start with Capital stock Figure 6.13

  33. Fig. 6.13 R MPK>1+r, so it is profitable to invest up to Marginal cost of capital MPK Output Output Capital stock Marginal productivity of capital Capital stock Figure 6.13

  34. Fig. 6.14 Technological progress Figure 6.14

  35. Fig. 6.14 R MPK We will start with an optimal capital stock... Output Output Capital stock Marginal productivity of capital Capital stock Figure 6.14

  36. Fig. 6.14 New MPK´ R Output Output Old Technological progress makes more output possible with the same capital stock. Desired capital stock increases. Capital stock Marginal productivity of capital MPK Capital stock Figure 6.14

  37. Funzione di investimento I è una qualche funzione della differenza tra K* e K corrente; dal momento che K è una funzione inversa di r, anche I dipenderà inversamente da r I = I(r)

  38. Modello accelerativo K* = vY I1 = K2* – K1* = v(Y2 – Y1) = vY2 v? Y = AK  MPK = Y/K Y/K = 1 + r K* = Y/(1+r) v = /(1+r) 2 < v < 3 I1 = vY2 + K1

  39. Modello della q di Tobin I prezzi delle azioni (PAZ) riflettono i profitti futuri Variazioni di PAZ sono una stima delle aspettative future dei profitti Tale stima dei profitti può differire dal prezzo dei beni capitali che costituiscono l’impresa, a volte definito costo di sostituzione di K

  40. Q di Tobin = valore di mercato di K/valore di sostituzione di K • I due valori possono differire per molti motivi, uno dato dai costi di aggiustamento • Quando q>1 vuol dire che il valore di mercato di K è superiore al costo (complessivo, cioè con i costi di aggiustamento) per acquisire e avviare un’impresa.

  41. Fig. 6.15 The q-theory of investment Investment 0 Tobin’s q 1 Figure 6.15

  42. Relazione tasso di interesse e q di Tobin • +r  - PAZ  - q • In generale, la q di Tobin sintetizza molte variabili; inoltre è rivolta al futuro; ruolo delle aspettative.

  43. Fig. 6.16(a) Investment and Tobin’s q:Inter-war Germany Figure 6.16(a)

  44. Fig. 6.16(b) Investment and Tobin’s q:Modern Germany Figure 6.16(b)

  45. Q di Tobin con costi di aggiustamento K2=I1

  46. K2 = I1+ (1-)K1

  47. Definiamo ora la q di Tobin come

  48. Allora possiamo riscrivere la condizione del 1 ordine come

  49. Fig. 6.17 C 1 MPK1 Tobin’s q=1 in a world of no adjustment costs If there were no costs of adjustment, the present value of the marginal cost of capital would be independent of the investment rate. Present value of MPK,cost of capital Note if there were no depreciation, the investment rate, I/K, = DK/K, the rate of change of the capital stock. Investment rate (I/K) (a) MPK=Marginal return of new investment Figure 6.17

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