經(jīng)管營銷簡單凱恩斯模型

1、.,1,簡單凱恩斯模型,.,2,思考題,國民收入(產(chǎn)出或GDP)由什么決定？,.,3,A Model With Many Names,Some economists refer to the Keynesian model as the “multiplier model” while other call it the aggregate production-aggregate expenditures model. We will use these names interchangeably as we show you how the development and applicat

2、ion of the basic Keynesian model gave birth to fiscal policy.,.,4,Fiscal Policy,Government Expenditures,Tax Changes,Stimulate,Contract,.,5,The Basic Keynesian Model,Provides a straightforward approach to using fiscal policy to close a recessionary gap. In theory, the model may be used to calculate v

3、ery precisely how much government spending must be increased, or taxes must be cut, to stimulate an economy back to full employment.,.,6,Some Important History: I,The General Theory of Employment, Interest and Money contains little resembling todays basic textbook Keynesian model. How Keynes arcane神

4、秘的 prose平鋪直敘的、乏味的文體、敘述 was transformed into an easily understood algebraic and graphical model is a story in and of itself involving two key figures, Professors Alvin Hansen and Paul Samuelson.,.,7,Some Important History: II,Alvin Hansen was a Classical economist who left the University of Wisconsin

5、 to take a post at Harvard and converted to Keynesianism. At Harvard, Hansen led a seminar that became an important cauldron 大鍋of ideas for the Keynesian doctrine. Hansen also took regular trips to Washington, D.C. to spread the Keynesian gospel真理準則信條 to the nations policymakers.,.,8,Some Important

6、History: III,Most importantly, Hansen wrote A Guide to Keynes which became the bible圣經(jīng) for economic students in the 1950s. Hansens star pupil Paul Samuelson wrote what would become the definitive macroeconomic textbook. Out of these writings has emerged the basic Keynesian model.,.,9,第一節(jié) 均衡產(chǎn)出,一，假設(shè)：

7、1、家戶和企業(yè) 2、總需求變動時，只會引起產(chǎn)量變動，使供求相等，而不會引起價格變動。,.,10,Keynesian Range,Aggregate Output,The Assumption Of Fixed Prices,Intermediate Range,Classical Range,Price Level,The most important assumption underlying this model is that prices are fixed. Keynes didnt believe this but did believe that when the economy

8、 is in the recessionary range, prices and wages were sufficiently inflexible so that income would adjust much faster than prices.,Potential Output,.,11,The Implication,The fixed price assumption allowed Hansen and Samuelson to develop a Keynesian model readily distinguishable from the aggregate supp

9、ly-aggregate demand model.,.,12,The Keynesian Model,Aggregate Expenditures,Real GDP, Output,AE=C+I+G+X,二，均衡產(chǎn)出：和總需求相等的產(chǎn)出。,IUO,IU0,100,.,13,第二節(jié)，消費函數(shù)理論,.,14,Aggregate Expenditures,Total spending or “aggregate expenditures” may be represented algebraically by the equation: AE=Consumption+Investment+Gove

10、rnment Expenditures+Net Exports The aggregate expenditures curve is simply the vertical summation of these four components.,.,15,Aggregate Expenditures,.,16,Aggregate Expenditures,Autonomous consumption happens independently of income,.,17,The Keynesian Expenditure Function,To fully understand how t

11、he Keynesian model works, we have to examine the major components of the Keynesian Expenditure Function: consumption, investment, government expenditures, and net exports.,.,18,Consumption,The largest component of aggregate expenditures. Accounts for almost 70% of total aggregate expenditures in the

12、 U.S.,.,19,Value of Category Category of 1996Percent consumption ($, billion)of total,Durable goods53812 Motor vehicles222 Household equipment212 Other104 Nondurable goods 1,35031 Food 658 Clothing and apparel237 Energy119 Other336 Services 2,50457 Housing628 Household operation251 Transportation170

13、 Medical care 681 Other773 _ _ Total, personal consumption expenditures 4,392 100,.,20,Autonomous Consumption,First, there is a level of consumption that occurs even if a person loses his or her job. This person will still be able to consume by dipping into savings. The level of consumption that occ

14、urs regardless of changes in ones income is called “autonomous consumption.”,.,21,Induced Consumption,Second, there is a level of “induced consumption” that will depend on the individuals disposable income. Disposable income is the amount of money you have left after paying taxes to the government.,

15、.,22,.,23,Marginal Propensity To Consume,Keynes described this behavior in terms of a persons “marginal propensity to consume” or “marginal propensity to expend.” This “MPC” is simply the extra amount that people consume when they receive an extra dollar of disposable income.,.,24,Marginal Propensit

16、y To Save,The marginal propensity to save or the marginal propensity to withdraw is simply the reciprocal of the MPC and it measures the extra amount people save when they receive an extra dollar of disposable income.,.,25,An Example,Some people may spend seventy five cents of every dollar of their

17、disposable income and save 25 cents. What will be the MPC and what would be the MPS?,.,26,An Example,In this case the marginal propensity to consume or MPC is .75 and the MPS is .25 In another situation, people may spend as much as 90 cents and save only ten cents of every dollar. In this case the M

18、PC is .90 and the MPS .10,.,27,MPS=5/20=0.25,MPC=15/20=0.75,The aggregate expenditures curve is flatter than the 45 degree line in the Keynesian model precisely because the MPC is less than one.,.,28,(1) (2) (3) (4) (5) Disposable incomeConsumptionMarginal propensityNet savingMarginal propensity (af

19、ter taxes) expenditures to consume ($) to save ($) ($) (MPC)(4)=(1)-(2) (MPS),A24,00024,110-110 890/1,000=0.89110/1,000=0.11 B25,00025,000 0 850/1,000=0.85150/1000=0.15 C26,000+150 750/1,000=0.75250/1,000=0.25 D27,000+400 640/1,000=0.64360/1,000=0.36 E27,240+760 590/1,000=0.59 F27,830+1,170 G30,0002

20、8,360+1,640,.,29,(1) (2) (3) (4) (5) Disposable incomeConsumptionMarginal propensityNet savingMarginal propensity (after taxes) expenditures to consume ($) to save ($) ($) (MPC)(4)=(1)-(2) (MPS),A24,00024,110-110 890/1,000=0.89110/1,000=0.11 B25,00025,000 0 850/1,000=0.85150/1000=0.15 C26,00025,850+

21、150 750/1,000=0.75250/1,000=0.25 D27,00026,600+400 640/1,000=0.64360/1,000=0.36 E28,00027,240+760 590/1,000=0.59410/1,000=0.41 F29,00027,830+1,170 530/1,000=0.53470/1,000=0.47 G30,00028,360+1,640,.,30,What It Looks Like,It can be expressed in an equation, a table or a graph. Algebraically, then, we

22、can represent the Keynesian consumption function simply as follows: c=a + MPC*Yd Total consumption, c, equals autonomous consumption, a, plus induced consumption where induced consumption equals the MPC times Yd .,.,31,The Consumption Function,slope=MPC,A,The slope of the consumption function is the

23、 MPC, or 0.75.,.,32,Consumption,消費函數(shù)：說明消費及其決定因素間的關(guān)系 決定因素：可支配收入、利率、對物價膨脹的預(yù)期、收入分配狀態(tài)等，其中最重要的是可支配收入 凱恩斯基本心理法則：一般而言，人們的消費隨者他們所得的增加而增加，但消費的增量低于所得的增量。 簡單消費函數(shù)： c=a+bYd a0, 0b1 a 為自發(fā)性消費，指由可支配所得以外因素所決定的民間消費，即可支配所得為零時的民間消費。 bYd為誘發(fā)性消費，指由可支配所得決定的消費。,.,33,邊際消費傾向與平均消費傾向,c=a+bYd APC=c/Yd MPC=c/Y APC=c/Yd= a/Yd+bb=M

24、PC,.,34,儲蓄函數(shù)與儲蓄傾向,儲蓄函數(shù)概念 儲蓄函數(shù)Saving Function 儲蓄與收入之間的依存關(guān)系。 遞增函數(shù)。 ss(y),.,35,儲蓄傾向,邊際儲蓄傾向Marginal Propensity to Save 增加的儲蓄在增加的收入中所占比例。,平均儲蓄傾向Average Propensity to Save 總儲蓄在總收入中所占比例。,.,36,線性儲蓄函數(shù),邊際儲蓄傾向（隨收入增加而增加）,隨收入增加而增加,.,37,s,0,s =a + (1b) y,y,線性儲蓄函數(shù),APS遞增，MPS不變 APSMPS,.,38,s,0,s =s(y),y,儲蓄曲線,平均儲蓄傾向遞

25、增，邊際儲蓄傾向遞增 APSMPS,APS0,APS0,A,.,39,消費函數(shù)與儲蓄函數(shù)的關(guān)系, ca + by s =a + (1b) y c+s= a+ bya +yby=y ycs APCAPS1 ycs MPCMPS1,.,40,消費函數(shù)與儲蓄函數(shù)的關(guān)系,c、 s,0,45,。,y,a, a,cc(y),ss(y),yc+s,.,41,結(jié)論,1、消費函數(shù)和儲蓄函數(shù)是互補的； 2、APC和MPC都隨收入的增加而遞減，且APCMPC；APS和MPS都隨收入增加而遞增，且APSMPS； 3、APC+APS=1 MPC+MPS=1,.,42,影響消費與儲蓄的因素,利率 對未來的預(yù)期 消費者保有

26、的流動性資產(chǎn)與其他資產(chǎn)的數(shù)量 物價水準 消費信用的條件與數(shù)量 收入分配的狀態(tài),.,43,絕對收入假說,上述關(guān)于消費與儲蓄的理論，實際上是凱恩斯的絕對收入假說。,.,44,第三節(jié) 消費函數(shù)理論的發(fā)展,凱恩斯的絕對收入假說 Absolute Income Hypothesis 杜森貝的相對收入假說 Relative Income Hypothesis 莫迪里安尼的生命周期假說 Life Cycle Hypothesis 弗里德曼的持久收入假說 Permanent Income Hypothesis,.,45,相對收入消費理論,影響消費的因素： 消費習慣（棘輪效應(yīng)） 相對收入水平（示范效應(yīng)）,消費函

27、數(shù)：,y,c,0,y1,y2,yt1,c1,c2,ct1,cs1,cs2,.,46,生命周期消費理論,青年,壯年,老年,觀點：人們把一生的收入在消費上作最佳分配,假定：工作期間WL，每年創(chuàng)造收入Y，退休以后無收入，生活年數(shù)NL（不包括父母撫養(yǎng)期）年消費C,工作期間儲蓄全部用于退休后消費,.,47,引入繼承財產(chǎn),影響生命周期消費的因素： 1、人口的年齡分布； 2、社會保障體系； 3、人們的消費理念,.,48,持久收入消費理論,k長期邊際消費傾向；,短期邊際消費傾向,-收入增加時，消費者不確定增加的收入在長期能否保持，因此不會將消費調(diào)到較高的消費水平。,影響消費的因素:1、消費同一生或持久收入相關(guān)

28、；2、暫時性收入變動對消費影響?。?、稅收政策：暫時性減稅對消費影響不大。,.,49,案例,我國的儲蓄問題 我國一直是一個儲蓄率很高的國家，截至2001年8月末，我國城鄉(xiāng)居民儲蓄存款余額為7.06萬億元，首次突破7萬億元大關(guān)，增長12.3%，增幅比上年同期高6.1個百分點，比上年底高5.4個百分點。8月份儲蓄存款增加881億元，比上年同月多增861億元。年累計儲蓄存款增加6254億元，比上年同期多增2748億元。其中，活期儲蓄增加2423億元，比上年同期少增415億元；定期儲蓄增加3661億元，比上年同期多增2396億元。定期儲蓄存款增加較多表明儲蓄存款穩(wěn)定性增強。,.,50,為了刺激我國的經(jīng)

29、濟增長，使大量的居民儲蓄向投資轉(zhuǎn)化，我國央行多次調(diào)整利息，2002年2月20日，中國人民銀行再次宣布，降低金融機構(gòu)人民幣存、貸款利率。這已經(jīng)是自1996年5月1日央行首次降息以來的第八次降息，但是實際效果并不明顯，我國的居民儲蓄還是呈不斷上升的勢頭。 問題： 1、解釋下列名詞：消費函數(shù)、儲蓄函數(shù) 2、根據(jù)所學的知識說明決定一國儲蓄率的原因，并簡要說明我國儲蓄率居高不下的原因。,.,51,案例的解答,一般來說，一國的儲蓄率主要是由以下幾方面原因決定的： （1）資本市場狀況。資本市場發(fā)達的國家，居民會把相當大部分的資金投向資本市場，從而降低儲蓄率。 （2）社會保障體系。如果一國的社會保障體系發(fā)達，

30、居民沒有后顧之憂，就會增加消費比率，從而儲蓄水平會較低。 （3）將來收入的保障情況。如果一國居民的將來收入有較強的保障，則儲蓄率就會較低，反之較高。 （4）一國居民的消費習慣。,.,52,案例的解答（續(xù)）,我國儲蓄率居高不下主要有以下幾方面原因： （1）我國社會保障體系落后。 （2）我國資本市場不發(fā)達。 （3）將來收入沒有保障。我國居民中農(nóng)民占絕大多數(shù)，他們將來的收入沒有保障，只能靠儲蓄積累資金。 （4）我國居民總體收入水平低。由于總體收入水平低，所以要考慮將來的各種支出，必然要提高儲蓄率。 （5）消費習慣使然。,.,53,第四 節(jié) 簡單凱恩斯模型,收入決定 假設(shè)：1、不考慮政府與外貿(mào)，經(jīng)濟是

31、封閉的。2、家庭不從事投資，并且投資數(shù)量是固定的常量，即i=i0,.,54,0,Y,450,c=a+by,a+i0,a,c+i= a+by+ i0,E,(a+ I0 )/(1-b),AD,總供給總需求法,收入決定圖解,.,55,使用儲蓄函數(shù)決定收入決定圖解,y=AD AD=c+i y=c+i y-c=i y-c=s s=i s=-a+(1-b)y -a+(1-b)y=i,.,56,收入決定圖解及調(diào)整過程（投資儲蓄法),I=I0,S=-a+(1-b)Y,I,-a,0,Y,E,(a+ I0 )/(1-b),.,57,第五節(jié) 乘數(shù)理論,1，投資乘數(shù)：收入的變化與帶來這種變化的投資支出的變化的比率。

32、y/ i =k dy/di=k,.,58,2,投資乘數(shù)的作用機制 i投資 就業(yè) 產(chǎn)量 收入 消費 刺激生產(chǎn) 就業(yè) 產(chǎn)量 收入 消費 刺激生產(chǎn) 就業(yè) 產(chǎn)量 第一輪收入增加，靠投資 i y1= i 第二輪收入增加，靠消費 c1=b y1 =b i y2= c1 =b i 第三輪收入增加，靠消費 c2=b y2 =b2 i y3= c2 = b2 i 第四輪收入增加，靠消費 y4= b3 i y= y1 + y2 + y3 + y4 + = i +b i +b2 i +b3 i + = i （1+ b + b2 + b3 ） = I/（1- b）,.,59,乘數(shù)理論,0,Y,E0a,E1a,E0,E

33、1,AE0= E0a +bY,AE1= E1a +bY,Y0,Y1,Ea,Y,Ea為自發(fā)性消費支出 Ea=Ca+I0 AE=總支出 AE=C+I= Ca+I0 +bY= Ea +bY,.,60,證明：,因為自發(fā)性支出等于自發(fā)性消費支出與自發(fā)性投資支出之和 因此二者的乘數(shù)都是1/(1-b),乘數(shù)：自發(fā)性支出變動導(dǎo)致均衡所得的數(shù)倍同方向變動，倍數(shù) 即為乘數(shù),.,61,節(jié)儉的矛盾,由乘數(shù)原理，自發(fā)儲蓄增加一單位（自發(fā)消費減少一單位），導(dǎo)致均衡收入減少1/(1-b)，但是根據(jù)S=-a+(1-b)Y，均衡收入減少一單位，誘發(fā)儲蓄減少(1-b)單位，那么，均衡收入減少1/(1-b)，導(dǎo)致誘發(fā)儲蓄減少1/(

34、1-b)*(1-b)=1，即儲蓄總量回到原來水平，儲蓄沒有變化，國民所得卻減少了。此為節(jié)儉的矛盾。 節(jié)儉的矛盾：若其他條件不變，整個社會增加儲蓄，使自發(fā)性儲蓄增加的結(jié)果，將使國民所得減少，失業(yè)增加，而儲蓄總量沒有增加。 兩點說明：第一，節(jié)儉有罪是凱恩斯模型的結(jié)論，具備凱恩斯模型的假設(shè)條件。第二，如果經(jīng)濟處于充分就業(yè)狀態(tài)，供給的增加可能需要技術(shù)或者資源使用量的增加。此時，儲蓄和節(jié)儉就是一種美德了。,.,62,第六節(jié) 三部門經(jīng)濟的收入決定及乘數(shù),一，政府收支與均衡收入 政府的收入與支出兩方面對宏觀經(jīng)濟活動都產(chǎn)生影響，下面先對政府收支做簡單說明，在探討引入政府部門以后，均衡所得（收入）的決定方式以及

35、政府收支對均衡所得的影響。 政府活動于國民收入決定相關(guān)者，最主要的有兩項： 政府的消費支出（除此之外，還有政府投資、對企業(yè)的補貼以及轉(zhuǎn)移性支付等也對宏觀經(jīng)濟活動產(chǎn)生影響） 政府的稅收（除了直接稅與間接稅外，還有政府財產(chǎn)與企業(yè)所得以及其他轉(zhuǎn)移收入）,.,63,Government Expenditures:,.,64,Government Expenditures:,Account for almost 20 percent of total aggregate expenditures. the Keynesian model assumes G to be autonomous so tha

36、t G simply equals autonomous government expenditures G0. As with the investment function, the government expenditure function can be graphically portrayed as a horizontal line.,.,65,Government Expenditures:,In general, government expenditures are less volatile易發(fā)生變動的 than investment (although episodi

37、c events系列事件 such as wars and natural disasters can lead to large fluctuations).,.,66,均衡所得（收入）決定,為簡化分析，有時我們將政府財產(chǎn)與轉(zhuǎn)移所得、補貼以及轉(zhuǎn)移性支出等合并到政府稅收內(nèi)，求得一個稅收凈額，并由政府決定，不隨意變動；政府投資與家庭、企業(yè)投資向合并，仍為外生變量。（G、T本來與Y相關(guān)）,.,67,.,68,與簡單凱恩斯模型相比： 乘數(shù)沒有變化 自發(fā)性支出發(fā)生了變化，多出了G0與T , TR G0與T對自發(fā)性支出的影響程度不同，可以由他們之前的符號看出。他們對Y的影響程度也不同。 稅收占自發(fā)性支出

38、的項目不是T而是bT(為什么？),T對自發(fā)性消費支出的增加產(chǎn)生反作用，并且為bT ，政府稅收凈額T對總需求的影響是間接通過可支配收入的變動產(chǎn)生的，對自發(fā)性消費支出的作用為bT，其余的(1-b)T被民間減少儲蓄的方式吸收。,.,69,二，各種乘數(shù),1，政府購買支出乘數(shù) dY/dG=kg =,.,70,2，稅收乘數(shù),dY/dT=kt =,.,71,3，政府轉(zhuǎn)移支付乘數(shù),dY/dTR=kTR =,.,72,4，平衡預(yù)算乘數(shù),政府支出增加完全依靠稅收增加給予彌補，而不通過舉債實現(xiàn)。 當政府支出與收入同時以相等數(shù)量增加或減少時，預(yù)算余額不受影響，這時國民收入變動與政府收支變動的比率，稱為平衡預(yù)算乘數(shù)。,

39、在封閉經(jīng)濟簡單凱恩斯模型中，平衡預(yù)算乘數(shù)等于1,.,73,.,74,Y0,Y1,Y*,0,C=a+b(Y-T),C+I=a+b(Y-T)+I0,C+I+G=a+b(Y-T)+I0+G0,a-bT+I0+G0,a-bT+I0,a-bT,E,.,75,三，比例稅情況下的乘數(shù),.,76,1，政府購買支出乘數(shù) dY/dG=kg =,.,77,2，稅收乘數(shù),dY/dT=kt =,.,78,3，政府轉(zhuǎn)移支付乘數(shù),dY/dTR=kTR =,.,79,4，平衡預(yù)算乘數(shù),政府支出增加完全依靠稅收增加給予彌補，而不通過舉債實現(xiàn)。 當政府支出與稅收凈額做同額度同方向變動時，預(yù)算余額不受影響，此種調(diào)整對均衡收入產(chǎn)生的

40、乘數(shù)效果，稱為平衡預(yù)算乘數(shù)。,.,80,dY/dG=dY/dT= 1,.,81,第七節(jié) 開放經(jīng)濟條件下的均衡收入決定,進出口需求的決定 出口需求決定因素：外國居民收入水平、本國產(chǎn)品相對價格、本國一般價格水平、匯率、出口退稅、補貼政策等 進口需求決定因素： 本國居民收入水平、進口品與本國產(chǎn)品比價、匯率及進口管制政策等 邊際進口傾向（MPI）與平均進口傾向(API) MPI為增加一單位收入（本國）所增加的進口數(shù)額。API為平均每單位收入中用于進口產(chǎn)品的比例。,.,82,Net Exports,.,83,Net Exports,Because exports create domestic prod

41、uction, income, and employment for an economy, they must be added to aggregate expenditures. However, when we purchase imports from a foreign country, no such production, income, or employment is created so that imports must be subtracted from aggregate expenditures.,.,84,.,85,開放經(jīng)濟條件下的均衡收入決定,.,86,比較

42、此式與封閉經(jīng)濟條件下的收入決定，不僅自發(fā)性支出多出了出口與進口之差額，乘數(shù)也由1/1-b（1-t）降低為1/1-b（1-t）+。 乘數(shù)之所以縮小，是因為在開放經(jīng)濟條件下，當收入增加一單位時，雖然使誘發(fā)性支出增加b（1-t）單位，但其中的單位所購買的是進口品，因此對本國國民產(chǎn)出的購買僅有b（1-t）- 單位，此時，乘數(shù)作用也由封閉經(jīng)濟中的1/1-b（1-t）變?yōu)殚_放經(jīng)濟中的 1/1-b（1-t）+ 。 兩點說明： 上述模型是極度簡化的凱恩斯模型，實際經(jīng)濟過程比這些模型復(fù)雜的多。上述推論的前提是價格水平不變，影響支出的因素除了收入之外，其他因素的影響沒有給與考慮，如利率、對未來的預(yù)期、流動性資產(chǎn)的

43、數(shù)量等。 上述分析所得到的乘數(shù)，除了比更完整的模型所求得的有所差異外，乘數(shù)效果的充分發(fā)揮也須假以相當時日。,.,87,題目,凱恩斯生平簡介 我國現(xiàn)行的財政政策 CPI的測量與計算 通貨膨脹的原因 通貨膨脹的效應(yīng) 我國現(xiàn)行的貨幣政策,.,88,C+I+G=a+b(Y-T0)+I0+G0,C+I+G+X-M=a+b(Y-T0)+I0+G0+X0-M0+Y),Y0,Y*,a-bT0+I0+G0+X0-Ma,a-bT0+I0+G0,.,89,A Simplifying Assumption,In the Keynesian model, whether the economy is in full e

44、mployment equilibrium will depend on the levels of the three other components of the aggregate expenditures curve: I, G, and net exports.,.,90,Investment,Investment expenditures include: purchases of residential structures, investment in business plant and equipment, and additions to a companys inve

45、ntory. Investment in plant and equipment is by far the biggest category, averaging a full 70 percent of total investment annually while total investment expenditures account for roughly 15 percent of total aggregate expenditures.,.,91,Investment,Assumed to occur independently of the level of income. Algebraically, this means I is equal to autonomous investment, Io. Therefore, the investm