1. 1 1 The classical model of macroeconomics

2. 2 Economics 122a Fall 2010 Agenda for this week: 1. The classical macro model (Chap 3) 2. How economists measure output/income (Chap 2)

3. Some announcements First problem set will be posted next week and due Wednesday Sept 22. Course is limited to those on course list on web page. I will post readings on logarithms on the course web page. There will probably be an optional section on logs and math review in the next couple of weeks. We will meet FRIDAY this week here, not Wednesday. Sections will begin next week Wednesday 4:50-4:50 and 5:00-5:50 Thursday 4:50-4:50 and 5:00-5:50 Thursday 7:00-7:50 and 8:00-8:50 3

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5. 5 This is our topic for today: classical approach

6. 6 Basics of Static Classical Model: Production Theory Classical production model. The basic model is simplest representation of the classical approach. When dynamized, it becomes the neoclassical growth model. Factor markets: capital and labor inputs (K and L) One sector for output (Y). Aggregate production function (for real GDP, Y) What is a production function? Recipe for combining inputs into outputs for given technology. (1)Y = F( K, L) Standard assumptions: positive marginal product (PMP), diminishing returns (DR), constant returns to scale (CRTS): CRTS: mY = F( mK, mL) PMP: ∂Y/∂K>0; ∂Y/∂L>0 DR: ∂ 2 Y/∂K 2 <0; ∂ 2 Y/∂L 2 <0

7. Production function for popovers 7 Courtesy of Florence Kling Harding, Twentieth Century Cookbook, 1921

8. Potential Output 8 Potential output. With exogenous labor force (LF), inherited capital (K), unemployment at the NAIRU (u*), this gives potential output (Y p ): (2) Y p = F[K, (1-u*)LF] Potential output critical for unemployment theory and growth theory and for medium and long-run forecasts. NAIRU (Mankiw “natural rate of unemployment”) = non-accelerating inflation rate of unemployment = unemployment rate at which inflation neither rises or falls = lowest sustainable rate of unemployment.

9. GDP loss in recession [potential minus actual output, billions of 2005 $] 9

10. 10 Example: Cobb-Douglas production function Very important production function: Cobb-Douglas (log linear) F( K, L) = AK α L 1-α Properties: MPL = ∂[AK α L 1-α ]/∂L=(1-α)AK α L 1-α /L = (1-α)Y/L = (1-α) x APL (and similarly for MPK)

11. 11 Factor Markets Factor markets: capital and labor inputs (K and L): -Capital inherited from past investments -Labor inputs exogenous (from biology, health, customs, pharma) Real wage rate : = W/P = MPL = ∂Y/∂L = ∂[F( K, L)]/∂L (see Fig. 1) Real rental rate on capital (like apartment rental as $ per month): = R/P = MPK = ∂Y/∂K = ∂[F( K, L)]/∂K National income = labor income + capital income = WL + RK Exhaustion of product theorem: With CRTS and competitive pricing, paying factors their marginal product leads income = output.

12. 12 Example: Cobb-Douglas production function National income Y = MPL x L + MPK x K = L[(1-α)Y/L] +K[αY/K ] = Y (exhaustion of product theorem) Shares of capital and labor: share of K = RK/Y = (αY/K ) x (K/Y) = constant = α Why do economists like Cobb-Douglas? See next slide.

13. 13 Near-constancy of labor’s share of national income

14. 14 What are the macroeconomic effects of immigration? Alfred Stieglitz

15. 15 L W/P MPL Real wages and MPL: graphics L* (W/P)*

16. 16 L W/P MPL Output = sum of the slices of MPL from 0 to L* L*

17. Calculus of marginal and total product Total product = sum of marginal products up to input level. 17

18. 18 L W/P MPL Neoclassical distribution of output/income L* (W/P)* Total wages Capital income* *More generally, all non-labor income Can reverse axes and get analogous results for capital.

19. 19 L W/P MPL Effect of immigration L* (W/P) 1 (W/P) 2 E1E1 E2E2 Assume immigrants are perfect substitutes for L Results: 1.Wage rate falls. 2.Output and national income rise. 3.Capital income rises. 4.More generally, income of substitutes fall and complements rise. 5.Empirical studies suggest that low-skilled and Hispanic workers are hurt by Mexican immigration.

20. 20 National Academy of Sciences study ( The New Americans ) “Immigration over the 1980s increased the labor supply of all workers by about 4 percent. On the basis of evidence from the literature on labor demand, this increase could have reduced the wages of all competing native-born workers by about 1 or 2 percent. Meanwhile, noncompeting native-born workers would have seen their wages increase…” “Based on previous estimates of responses of wages to changes in supply, the supply increase due to immigration lowered the wages of high school dropouts by about 5 percent…”

21. 21 Other applications of static neoclassical model Impact of foreign investment : Assume that foreign firms build a factory in US. What is effect in simple neoclassical model? Answer: Same as immigration, but reverse the factors. Impact of government debt: What is the effect of a growing government debt? Slightly more complicated, but might crowd out capital stock. This then reduces output. Note effects on wages and rentals.

22. 22 Next class on Friday: Chapter 2 “Just what is this ‘Y’?” “Just how do we measure GDP and real GDP?”