中級宏觀經(jīng)濟(jì)學(xué)_Ch3_國民收入.ppt

1、slide 0,第三章 國民收入：源于何處，去向何方,宏觀經(jīng)濟(jì)學(xué)（第6版） （美） 曼 昆 任課教師 任力,slide 1,在這一章，你將會學(xué)到：,什么決定了經(jīng)濟(jì)的總產(chǎn)出（或總收入） 生產(chǎn)要素的價格是如何決定的 總收入是如何分配的 什么決定了對商品與服務(wù)的需求 商品市場的均衡是如何實(shí)現(xiàn)的,slide 2,模型概要,封閉經(jīng)濟(jì)，市場出清 供給方 市場因素(供給，需求，價格) 決定產(chǎn)出或收入 需求方 決定 C, I, G。 均衡 商品市場 可借貸的資本市場,slide 3,生產(chǎn)要素,K = 資本， 用于生產(chǎn)的工具，機(jī)器，廠房等等 L = 勞動， 包括體力和腦力勞動者,slide 4,生產(chǎn)函數(shù),可表示

2、為：Y = F (K, L) 表明經(jīng)濟(jì)由K單位資本和L單位勞動能夠有多少單位的產(chǎn)出（Y） 反映了經(jīng)濟(jì)技術(shù)水平。 表明規(guī)模報酬不變。,slide 5,規(guī)模報酬： 復(fù)習(xí),設(shè)最初生產(chǎn)函數(shù)為： Y1 = F (K1 , L1 ) 假如所有的投入要素都擴(kuò)大（減少）Z倍： K2 = zK1 and L2 = zL1 (如果 z = 1.25， 那么，所有的投入都增長 25%) 這時，產(chǎn)出會發(fā)生什么變化， Y2 = F (K2 , L2 ) ? 如果規(guī)模報酬不變，則Y2 = zY1 如果規(guī)模報酬遞增，則Y2 zY1 如果規(guī)模報酬遞減，則Y2 zY1,slide 6,練習(xí)：決定下列函數(shù)的規(guī)模報酬,判斷下列生產(chǎn)

3、函數(shù)是規(guī)模報酬不變、遞增還是遞減？,slide 7,模型的假設(shè)前提,不考慮技術(shù)進(jìn)步因素。 資本與勞動的供給固定不變，即：,slide 8,GDP 的決定,產(chǎn)出是指在供給要素不變、技術(shù)水平不變的條件下的產(chǎn)出：,slide 9,國民收入的分配,由要素價格及生產(chǎn)要素的單位價格決定 工資是勞動的價格 租金率（利率）是資本的價格,slide 10,符號說明：,W = 名義工資 R = 名義租金率 P = 產(chǎn)出的價格 W /P = 實(shí)際工資 (用于衡量單位產(chǎn)出) R /P = 實(shí)際租金率,slide 11,要素價格是如何決定的,要素價格是由市場的供給與需求因素決定的。 回顧：每種要素的供給是固定的 需求的

4、情況怎么樣?,slide 12,The distribution of national income is determined by factor prices. Factor prices are the amounts paid to the factors of productionthe wages workers earn and the rent the owners of capital collect. Because we have assumed a fixed amount of capital and labor, the factor supply curve i

5、s a vertical line. The next slide will illustrate.,Recall that the total output of an economy equals total income. Because the factors of production and the production function together determine the total output of goods and services, they also determine national income.,How is National Income Dist

6、ributed to the Factors of Production?,slide 13,The price paid to any factor of production depends on the supply and demand for that factors services. Because we have assumed that the supply is fixed, the supply curve is vertical. The demand curve is downward sloping. The intersection of supply and d

7、emand determines the equilibrium factor price.,FACTOR PRICES,slide 14,To make a product, the firm needs two factors of production, capital and labor. Lets represent the firms technology by the usual production function: Y = F (K, L) The firm sells its output at price P, hires workers at a wage W, an

8、d rents capital at a rate R.,Capital,Labor,slide 15,slide 16,The Firms Demand for Factors,We know that the firm will hire labor and rent capital in the quantities that maximize profit. But what are those maximizing quantities? To answer this, we must consider the quantity of labor and then the quant

9、ity of capital.,slide 17,The Marginal Product of Labor,The marginal product of labor (MPL) is the extra amount of output the firm gets from one extra unit of labor, holding the amount of capital fixed and is expressed using the production function: MPL = F(K, L + 1) - F(K, L). Most production functi

10、ons have the property of diminishing marginal product: holding the amount of capital fixed, the marginal product of labor decreases as the amount of labor increases.,Diminishing Marginal Product of Labor,Y,L,The MPL is the change in output when the labor input is increased by 1 unit. As the amount o

11、f labor increases, the production function becomes flatter, indicating diminishing marginal product.,slide 18,From the MPL to Labor Demand,When the competitive, profit-maximizing firm is deciding whether to hire an additional unit of labor, it considers how that decision would affect profits. It the

12、refore compares the extra revenue from the increased production that results from the added labor to the extra cost of higher spending on wages. The increase in revenue from an additional unit of labor depends on two variables: the marginal product of labor, and the price of the output. Because an e

13、xtra unit of labor produces MPL units of output and each unit of output sells for P dollars, the extra revenue is P MPL. The extra cost of hiring one more unit of labor is the wage W. Thus, the change in profit from hiring an additional unit of labor is D Profit = D Revenue - D Cost = (P MPL) - W,sl

14、ide 19,Thus, the firms demand for labor is determined by P MPL = W, or another way to express this is MPL = W/P, where W/P is the real wage the payment to labor measured in units of output rather than in dollars. To maximize profit, the firm hires up to the point where the extra revenue equals the r

15、eal wage.,The MPL depends on the amount of labor. The MPL curve slopes downward because the MPL declines as L increases. This schedule is also the firms labor demand curve.,slide 20,The firm decides how much capital to rent in the same way it decides how much labor to hire. The marginal product of c

16、apital, or MPK, is the amount of extra output the firm gets from an extra unit of capital, holding the amount of labor constant: MPK = F (K + 1, L) F (K, L). Thus, the MPK is the difference between the amount of output produced with K+1 units of capital and that produced with K units of capital. Lik

17、e labor, capital is subject to diminishing marginal product. The increase in profit from renting an additional machine is the extra revenue from selling the output of that machine minus the machines rental price: D Profit = D Revenue - D Cost = (P MPK) R. To maximize profit, the firm continues to re

18、nt more capital until the MPK falls to equal the real rental price, MPK = R/P. The real rental price of capital is the rental price measured in units of goods rather than in dollars. The firm demands each factor of production until that factors marginal product falls to equal its real factor price.,

19、The MPK and Capital Demand,slide 21,The Division of National Income,The income that remains after firms have paid the factors of production is the economic profit of the firms owners. Real economic profit is: Economic Profit = Y - (MPL L) - (MPK K) or to rearrange: Y = (MPL L) - (MPK K) + Economic P

20、rofit. Total income is divided among the returns to labor, the returns to capital, and economic profit. How large is economic profit? If the production function has the property of constant returns to scale, then economic profit is zero. This conclusion follows from Eulers theorem, which states that

21、 if the production function has constant returns to scale, then F(K,L) = (MPK K) - (MPL L) If each factor of production is paid its marginal product, then the sum of these factor payments equals total output. In other words, constant returns to scale, profit maximization,and competition together imp

22、ly that economic profit is zero.,slide 22,Paul Douglas,Paul Douglas observed that the division of national income between capital and labor has been roughly constant over time. In other words, the total income of workers and the total income of capital owners grew at almost exactly the same rate. He

23、 then wondered what conditions might lead to constant factor shares. Cobb, a mathematician, said that the production function would need to have the property that:,Capital Income = MPK K = Labor Income = MPL L = (1- ) Y,slide 23,勞動的需求,假定市場是完全競爭的： 即：每個廠商面臨的W, R和P 都是給定的 基本思想：如果成本小于收益，那么廠商就會增加勞動雇傭。 成本

24、= 實(shí)際工資 利潤= 勞動邊際產(chǎn)品價值,slide 24,勞動的邊際產(chǎn)品 (MPL),定義:廠商運(yùn)用額外的一單位勞動投入能夠生產(chǎn)出來的一單位產(chǎn)出: (假定其它投入不變): MPL = F (K, L +1) F (K, L),slide 25,練習(xí): 計算并繪MPL圖,計算每一個勞動投入量L上的 MPL 畫出生產(chǎn)函數(shù)圖 繪出 MPL 曲線圖（其中橫軸表示勞動投入量L，縱軸表示MPL）,LYMPL 00n.a. 110? 219? 3278 434? 540? 645? 749? 852? 954? 1055?,slide 26,答案：,slide 27,Y 產(chǎn)出,生產(chǎn)函數(shù)與MPL,L 勞動,M

25、PL,slide 28,邊際報酬遞減,隨著某種要素投入的增長，它的邊際產(chǎn)品價值是遞減的 (當(dāng)其它條件不變時)。 我們可以直觀感覺一下：固定資本K，當(dāng)投入的勞動L增長時： 每個工人擁有的機(jī)器數(shù)量減少 更低的勞動生產(chǎn)率,slide 29,檢查一下你的理解力：,下列那一個生產(chǎn)函數(shù)對勞動是邊際報酬遞減的？,slide 30,第二部分練習(xí),假定 W/P = 6。 如果廠商現(xiàn)有勞動量 L = 3， 那么廠商是應(yīng)該雇傭更多還是更少的勞動？為什么？ 如果廠商現(xiàn)有勞動量 L = 7，那么廠商是應(yīng)該雇傭更多還是更少的勞動？為什么？,LYMPL 00n.a. 11010 2199 3278 4347 5406 64

26、55 7494 8523 9542 10551,slide 31,勞動需求與MPL,廠商雇傭勞動的數(shù)量達(dá)到最佳點(diǎn)時： MPL = W/P,slide 32,租金率的決定,剛才我們已經(jīng)理解了 MPL = W/P， 資本也遵循同樣的邏輯 MPK = R/P ： 資本的邊際報酬遞減： 當(dāng)使用資本K 時MPK MPK曲線是廠商對資本的需求曲線。 廠商利潤最大化時擁有的資本量必然使： MPK = R/P。,slide 33,新古典分配理論,每種投入的要素都獲得其邊際產(chǎn)品價值 被許多經(jīng)濟(jì)學(xué)家所認(rèn)可,slide 34,收入是如何分配的：,總勞動收入 =,如果生產(chǎn)函數(shù)是規(guī)模報酬不變的，那么：,總資本收入 =,

27、slide 35,模型概述,封閉經(jīng)濟(jì)，市場出清 供給方 市場因素 (供給，需求，價格) 產(chǎn)出/收入的決定因素 需求方 C, I 和 G 的決定因素 均衡 商品市場 資本借貸市場,DONE ,DONE ,Next ,slide 36,對商品與服務(wù)的需求,總需求的組成： C = 消費(fèi)者對g & s的需求 I = 對投資品的需求 G = 政府對g & s的需求 (封閉經(jīng)濟(jì)時：沒有凈出口NX ),slide 37,消費(fèi)， C,定義：可支配收入是指總收入減去總稅收： Y T 消費(fèi)函數(shù)： C = C (Y T ) 表明： (Y T ) C 定義：邊際消費(fèi)傾向是指當(dāng)可支配收入增加一單位時，消費(fèi)C的增加量,s

28、lide 38,消費(fèi)函數(shù),slide 39,投資， I,投資函數(shù)指： I = I (r ), 這里，r 指實(shí)際利率， 即名義利率剔除通貨膨脹。 實(shí)際利率是： 借款成本 使用自有資本投資時的機(jī)會成本。 因此，r I,slide 40,投資函數(shù),slide 41,政府支出， G,G 包括政府用于商品與服務(wù)上的支出。 G 不包括轉(zhuǎn)移支付 一般假定政府支出與稅收是外生給定的，即：,slide 42,商品與服務(wù)市場,實(shí)際利率的變化使得需求等于供給。, 總需求：, 總供給：, 均衡：,slide 43,資本借貸市場,一個金融系統(tǒng)的簡單的供需模型。 將“可借貸的資金”看作一種資產(chǎn)： 資金的需求是投資 資金的

29、供給是儲蓄 實(shí)際利率是資金的“價格”,slide 44,資金的需求：投資,可貸資金的需求: 來自投資:廠商為建造廠房、辦公大樓以及購置設(shè)備、辦公用具等而進(jìn)行的借款融資行為。 消費(fèi)者的購房借款。 投資與利率負(fù)相關(guān)， 也即可貸資金的“價格”（借款成本）。,slide 45,資金的需求曲線,投資曲線也就是可貸資金的需求曲線。,slide 46,資金的供給：儲蓄,可貸資金的供給來自于儲蓄： 家庭 把他們的資金存入銀行、購買債券及其它資產(chǎn)，從而形成廠商投資時可以借貸的資金。 當(dāng) 政府 獲得的稅收收入沒有全部支出時也會形成儲蓄。,slide 47,儲蓄的類型,私人儲蓄 = (Y T ) C 公共儲蓄 =

30、T G 國民儲蓄， S = 私人儲蓄 + 公共儲蓄 = (Y T ) C + T G = Y C G,slide 48,符號說明： = 變量的變化,對任意變量X，X = “X 的變化量 ” 是希臘字母Delta（大寫）,例如： 如果 L = 1 并且 K = 0, 那么 Y = MPL。 更一般地講，如果 K = 0, 那么,(YT ) = Y T , 因此 C = MPC (Y T ) = MPC Y MPC T,slide 49,練習(xí)：計算儲蓄的變化量,假定 MPC = 0.8、 MPL = 20。 對于下列每一種情況，計算S ： G = 100 T = 100 Y = 100 L = 1

31、0,slide 50,答案：,slide 51,專欄： 預(yù)算盈余與預(yù)算赤字,當(dāng) T G 時， 預(yù)算盈余 = (T G ) = 公共儲蓄 當(dāng) T G 時， 預(yù)算赤字 = (G T )這時，公共儲蓄是負(fù)的。 當(dāng)T = G 時， 預(yù)算平衡，公共儲蓄 = 0。,slide 52,美國聯(lián)邦政府預(yù)算,(T-G)占GDP的百分比,占GDP百分比,slide 53,美國聯(lián)邦政府赤字,小知識：在 1990 年代早期， 每取得1美元稅入，大約有18美分用于償債。 (現(xiàn)在，這個數(shù)字大約是9美分。),slide 54,可貸資金的供給曲線,國民儲蓄并不依賴?yán)蕆,因此，供給曲線是垂直的。,slide 55,可貸資金的市場均衡,slide 56,利率 r 的特殊性,r 可使商品市場與資本市場同時達(dá)到均衡： 如果資本市場是均衡的，那么： Y C G = I 等式兩邊同時加上(C +G )可得： Y = C + I + G (說明商品市場均衡) 因此，,slide 57,專欄：精通模型,要想深入地理解一個模型，必須做到： 明確那個變量是內(nèi)生的，那個變量是外生的。 對圖形中的每條曲線，應(yīng)該了解： 定義 對曲線斜率的直覺 所有影響曲線移動的因素 運(yùn)用模型分析2項c目中變量的影響效果。,slide