S tranh lun gia cc trng phi trong l thuyt kinh t v mNguyn Hoi Bo 28/6/2005 (First Draft)

Tm tt Bi vit im li cc quan im v tranh lun trng tm ca cc trng phi trong l thuyt kinh t v m t c in n nay. Mt cch tng qut, cc trng phi kinh t bt u xut hin khi l thuyt ca Keynes ra i vo u th k 20. Theo , trc Keynes chng ta c cc l thuyt ca trng phi c in, sau Keynes chng ta c trng phi C in Mi v Keynes Mi. Nu nhng nh kinh t trong trng phi C in Mi vn trung thnh trong khun kh phn tch ca Walras ngha l cn bng tng th ng thi vi gi nh rng th trng l hon ho th ngc li, nhng nh kinh t trong trng phi Keynes Mi thng phn tch ngoi khun kh y, vi cc m hnh nh trong tnh hung th trng tht bi. Hai dng quan im ny vn cn tip din cho n ngy nay. im chung duy nht l tt c cc ng gp cho l thuyt kinh t v m gn y u xy dng trn nn tng kinh t vi m. Cho d cc l thuyt c tinh lc v pht trin khng ngng t hn hai th k qua, nhng vic gii thch hai cu hi cn bn (1) nguyn nhn no c s giao ng trong sn lng v nhn dng v (2) v chng ta phi lm g trong trung hp c s giao ng ? vn cha c cu tr li tho ng.

Khoa Kinh t Pht trin, i hc Kinh t TP HCM. Email: nguyenhoaibao@gmail.com

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a s cc trng i hc kinh t hng u khng cn dy lch s cc t tng kinh t na. Tuy nhin, nhng nh kinh t hc li lc th li thng xuyn lit k ra hng t nhng t tng to lao va mi pht trin m trong chng lc no cng ht sc bng by. Ri cng vi cc nh kinh t ny, h dy chng ta bit cc ch th kinh t ti a li nhun ca h nh th no. Lch s t tng cc hc thuyt kinh t ghi li nhng tin trin ca hiu bit , nhng chng ta kh m bit c lch s kinh t nh th no nu khng c s h tr bng thc nghim ca s liu theo thi gian (David Laidler 2001).

Gii thiu Thut ng kinh t hc economic bt ngun t ch oeconomicus trong gio trnh qun l v lnh o hiu qu ca Xenophon t thi Hy Lp c i, tc khong nm 500 trc cng nguyn (Ekelund 2004). Nhng n ch tht s c h thng ho mt cch c bn bi nh kinh t hc c in Adam Smith trong tc phm S giu c ca cc quc gia (The Wealth of Nations) xut bn ln u nm 1776. T n nay hn ba th k, cc l thuyt kinh t v m (macroeconomic1) pht trin rt xa so vi nhng g nguyn thu ca n song vn xoay quanh hai cu hi cn bn m cng t khi ngun cho cc trng phi v s tranh lun: (1) ti sao c s giao ng trong sn lng (production) v mc nhn dng (employment); (2) chnh sch hp l g l khi c s giao ng ? Tr li cho hai cu hi ny khi ngun cho hai trng phi cn bn m s bt ng ca h vn cn dai dn cho n ngy nay: Trng phi C in (Classical Economics) m sau ny c tip sc bi nhng nh kinh t gi l trng phi Tn C in (Neoclassical Economics) v by gi l C in Mi (New Classical Economics). Nhm ny nhn nn kinh t v c bn l c tnh cht n nh v c xu hng tin ti trng thi cn bng khi c giao ng. Tc c xu hng t iu chnh v trng thi m t c sn lng tim nng v t l tht nghip t nhin. Tng trng kinh t v vic lm c xc nh bi s thay i ca cng ngh. Chnh cch nhn ny, h cho rng nh nc khng cn can thip vo cc hot ng kinh t. Ngc li, nhm i lp c khi xng bi th lnh l John Maynard Keynes (hay cn gi l trng phi ca Keynes Keynesian economics).Bt u t nhng nm 1940 th thut ng kinh t v m (macroeconomic) mi xut hin. Bi bo u tin s dng t macro-economics l ca De Wolff vo nm 1941, Income elasticity of demand, a micro economics and a macro economics interpretation. Sau t macroeconomics xut hin ln u trong bi Macroeconomics and the theory of rational behavior ca Klein nm 1946 (Blanchard 2000).1

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Nhng nh kinh t sau ny tip tc gi ngn c ca Keynes c gi l trng phi Keynes Mi (New Keynesian Economics). i vi h, nn kinh t c tnh cht khng n nh, tng trng l kt qu ca s giao ng, th trng lao ng khng cn bng. Chnh s khng n khp ny thng dn n s v nn kinh t. V vy, h ng h mnh m s vai tr can thip ca chnh ph trong hot ng kinh t. V cch tip cn, cc nh kinh t trong trng phi c in t trc n nay lun c gng gii thch s giao ng kinh t trong khun mu cn bng tng qut ca Walras (Walrasian paradigm). c c iu ny quan im ca h cho rng cc th trng l hon ho v v th lun t ti u Pareto. Ngc li, t Keynes tr i th cho rng th trng l tht bi v s dao ng l phn nh khng t c ti u Pareto. Trng phi Keynes Mi gn y thng s dng cc m hnh nh (small model) phn tch cn k nhng vn m h quan tm ch khng tip cn bng cc m hnh y mang tnh l thuyt phc tp. Mc d c hai u tin ti phn tch v m trong nn tng ca kinh t vi m (micro-foundation). Nu nhn cc t tng kinh t nh l dng chy, th Keynes ng vai tr nh mt ng ba. Theo , trc Keynes chng ta c cc nh kinh t hc c in (v tn c in). Sau Keynes, bt u gia cui nhng nm 1970, r ra hai dng chy ln: New Classical Economics v New Keynesian Economics. Cc tng cn bn m nhng hu du New Classical Economics pht trin nhm bo v quan im truyn thng ca h l: l thuyt trng tin (monetarism), k vng hp l (rational expectation), l thuyt chu k kinh doanh thc (real business cycle theory), tng trng tn c in (neoclassical growth theory), l thuyt la chn cng cng (public choice theory), trng phi trng cung (suply side economics). i vi nhm New Keynesian Economics c cc nhnh nh hn nh nh ch (institutionist), hu Keynes (Post Keynesian Economics), l thuyt tng trng ni sinh mi (New Endogenous Growth theory). V mt thi gian, cch mng v l thuyt tng qut ca Keynes l t 1930 1940, sau l cuc chin gia nhng ngi theo trng phi trng tin (monetarist) v trng phi Keynes trong khong thi gian 1950-1960. Thp nin 70 l s bng n ca cc pht kin xung quanh khi nim k vng hp l (rational expectation) v t nhng nm 1980 tr v y l s dng gia trng phi Keynes Mi v C in Mi (Blanchard 2000).

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Phn cn li ca bi vit ny, chng ti c gng ln lt im qua nhng tng trng tm ca tng trng phi. L thuyt kinh t v m pht trin rt rng v nhiu phc tp, chng ti ch c gng nu nhng im chnh nht trong dng t tng ca tng trng phi v quan tm n xu hng (mainstream) ca s tin trin 2. Chng ta s thy rng, ci ngun xut pht ca tng trng phi u c nhng bi cnh lch s v h t tng v nn tng ca trit hc, nht l giai on ban u. S pht trin ca k thut phn tch thc nghim v s liu theo thi gian cng gp phn ng k, nu khng ni l quyt nh n vng i ca cc l thuyt. Trong bi vit ny, kinh t v m cng ch c nh ngha gii hn trong vic phn tch s giao ng sn lng v nhn dng. Chng ti khng phn tch tng trng v kinh t chnh tr trong kinh t v m. Vic gii hn nh vy s khng nh hng n mc ch ca bi vit nhng gip chng ta nhn ra vn trng tm r hn, t nht trong khun kh ca mt bi vit ngn. Trng phi c in Trong cc nh kinh t hc c in th Adam Smith, David Ricardo v Thomas Malthus nh l nhng i din trung tm cho nn tng phn tch v m3. H sinh ra v trng thnh trong giai on m cc nh trit gia phng Ty gi l thi k Khai sng

S tin trin ny nu nhn theo gc thi gian, Blanchard cho rng c th chia thnh 3 giai on cn bn. Giai on th nht l trc nhng nm 1940, y l thi k khm ph, kinh t v m khng hn l kinh t v m nh by gi. L thuyt v tin t v chu k kinh doanh l hai lnh vc tch ring, s hiu bit v nn kinh t l cha tht r rng v khng c mt khun kh phn tch tng th. Giai on th hai l t 1940 n 1980, y l giai on hnh thnh c mt khun kh hp nht gia tin t v sn lng, bt u bng m hnh IS LM. S phn tch cn bng tng th cng mang tnh ng v nhn r hn cc c sc cng nh c ch ca s giao ng. Tuy vy, cng theo gt chn Achille, vic gii quyt vn cng cn h hng v khng quan tm n cc yu t khng hon ho ca th trng. Giai on t nm 1980 n nay, y l mt thi k khm ph mi, tho lun cc vn v khng hon ho trong kinh t v m nh mi quan h gia tin lng danh ngha v s n nh gi c, thng tin khng cn xng, th trng khng hon ho V l giai khm ph nn mi th li bt u ln xn! (Blanchard 2000) Cc nh kinh t hc c in cui th k 19 u th k 20 c gi l neo-classical economics, nh John Stuart Mill (1806 1873), Alfred Marshall (1842-1924), Lon Walras (1834-1910), Vilfredo Pareto (18481923) c ng gp rt ln trong xy dng l thuyt kinh t hc. Tuy vy, phn ln h tp trung vo phn tch cc vn vi m hn l nhng m hnh mang tnh tng qut phn tch nn kinh t. Irving Fisher (1867-1947) da trn tung ca cn bng tng th ca Walras, Pareto m h thng ho thnh nn tng l thuyt cho phn tch kinh t v m m ngy nay chng ta thng gi l l thuyt c in. Richard Cantillion (1680?-1734), Henry Thornton (1760-1815), David Hume (1711 -1776), Fisher, Knuth Wicksell (18511926) l nhng i din ch yu trong xy dng v pht trin l thuyt tin t.3

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(Enlightenment)4, tc l giai on ca th ca 17, 18. Chnh v th, cc nh kinh t hc c in u b nh hng mnh m bi t tng ca cc nh trit hc ng thi v h th hin nh hng qua quan im cng nh cc l thuyt m h xy dng. Cc trit gia li lc thi khai sng l Voltaire, Rousseau, Loke, Hume v Kant. Tt c h theo quan im duy vt v v thn, trit hc trn c s l tr thay v thn hc trn c s nim tin. H ng h cho s t do cc nhn v phn i cc thit ch lm tn hi n s t do y. Theo Kant Khai sng l s thot ly ca con ngi ra khi tnh trng v thnh nin do chnh con ngi gy ra. V thnh nin l s bt lc khng th vn dng tr tu ca mnh mt cch c lp m khng cn s ch o ca ngi khc Hy c can m s dng tr tu ca chnh mnh! l phng chm ca Khai Sng5 Cc nh kinh t hc c in cng vy, v quan im ct li, h ng h thng mi t do v hn ch cng nhiu cng tt v vai tr ca nh nc vo hot ng kinh t6. i vi cc nh kinh t c in h ch quan tm n cc nhn t thc (real factor), chng hn nh sn xut ch khng phi l cn cn thanh ton nh thi ch ngha trng thng, theo h mi l du hiu ca s thnh vng. Cn nhng khi vng m quc gia tch lu c ch l du hiu cho thy m bo s an ninh ca chnh ph m thi. T tng tn trng c nhn tuyt i ng thi nh phn nh r trong l thuyt m Smith xy dng. Theo ng th chnh ci hnh vi t li (self-interested) ca mi con ngi thng qua trao i s t ng lm cho tng th nn kinh t tt hn, ch khng phi l can thip. Smith gi l bn tay v hnh (invisible hand). iu ny cng ng rng th trng t do l t n em n hiu qu.

C th ni trong lch s trit hc u chu, cha c mt tro lu t tng no rc r v si ni nh tro lu khai sng trong khong gia th k 18, mt tro lu c th ca t tng Ty u nht l Anh, Php v c: ti Php th k th 18 c xem l thi i ca nh sng (le sicle des lumires), ti Anh, khai sng c xem l Enlightenment, chiu sng hay gic ng v ti c Aufklrung, khai sng. Nhng danh hiu ny thot tin ni ln nim lc quan nm trong t tng con ngi th k th 18: bng ti ca huyn thoi, gio iu, m tn, lc hu, chm tin, bt cng, p bc ngn cn bc pht trin ca con ngi trn tt c cc lnh vc x hi, chnh tr, vn ha, tn gio, khoa hc ca qu kh b nh tan, nhng bc cho nh sng ca L tr v Tin b (Lan, 2004)5 6

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I. Kant, Tr li cu hi: Khai sng l g? (trch li t Lan 2002)

iu ny ngc hn vi nhng vi Ch ngha Trng thng (Mercantilist) trc h. Nhng ngi theo ch ngha trng thng cho rng mt quc gia hng cng thng qua s tch lu ca ci, m c bit l vng. H ch trng phi lm sao ngy cng thng d trong ci cn thanh ton. t c nh vy h c v cho thu quan, qun l trao i v c quyn thng mi.

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Trong nhiu ng gp ca cc nh kinh t hc c in v sau ny l tn c in trong l thuyt kinh t v m c th chia thnh hai ni dung ln: l thuyt tin t (monetary theory) v l thuyt chu k kinh doanh (business cycle theory)7. Nhng c hai lnh vc dng nh khng c ni kt vi nhau bi v c s phn bit gia cc bin s thc v bin s danh ngha m sau ny c bit n bng thut ng kinh in l s phn i c in (classic dichotomy). Theo h, cc bin s thc (real variable) th c xc nh bi cc bin s thc ring l khc, cn bin s tin t th ch c xc nh bi cc bin s tin t m thi. iu ny cng ng rng chnh sch tin t (monetary policy) ch c th lm thay i mc gi tng qut (general price) ch khng th nh hng n tin lng thc (real wage), sn lng (production) v nhn dng (emloyement). Gi thuyt trng tm ca h l mc gi tng qut v tin lng danh ngha l hon ton linh hot. V nh s linh hot ny lm cho cc bin s thc khng thay i v th trung lao ng lun t trng thi cn bng ton dng. Kt qu ca cc bin s danh ngha linh hot ny cng to lp c trng thi cn bng n nh pha tng cu, ngha l sn lng lun tng ng vi sn lng ton dng. Cch l gii ny cn c bit n vi tn gi l lut Say (Saylaw). Theo cc trng phi c in, ngay c khi m tin lng danh ngha cng nht, mt c sc lm gim tng cu s lm cho mc gi gim xung cng hm rng tin lng thc tng ln. Cho d trong giai on c t l tht nghip tng ln nhng th trng lao ng vn t c hiu qu ng vi mc tin lng cao . Vi quan im nh trn, cc nh kinh t hc c in ch tp trung vo vic lm cch no tng trng cao nht ch khng phi l gii quyt vn mt cn bng trong nn kinh t. H tht ra cng quan tm n cc trng hp nn kinh t lch khi trng thi cn bng, ngha l khng t c sn lng tim nng v tht nghip t nhin, nhng cho rng ch l nhng giao ng nht thi, l mt c sc ngu nhin no chng hn nh chin tranh, thi tit xu lm ma v tht bi nhng cc bin s danh ngha s linh hot iu chnh nn kinh t tr v trng thi cn bng nhanh chng.

Thc ra l cch gi theo ngha hin i nh by gi, nh ni lc u kinh t v m tht s xut hin mt cch trit sau Keynes.

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Mt im kt ni rt ng ch ca l thuyt c in m sau ny, c l, Keynes nhn ra v khai thc l phn tch ca Wicksell. ng phn bit c hai li sut trong nn kinh t, l li sut t nhin (natural rate of interest) v li sut tin t (money rate of interest). Li sut t nhin theo Wicksell l li sut trn vn (capital) cn li sut tin t l li sut ca tri phiu (bonds). Phn tch ny cho thy mm mng phn tch trn cc th trng hng ho (ni m li sut trn vn c xc nh) v th trng tin t (ni m li sut trn tri phiu c xc nh) bt u hnh thnh. l mt im tin cc l thuyt t Keynes tr i bt u gn kt gia l thuyt tin t v chu k kinh doanh. Tuy nhin mt thp nin trc khi tc phm ca Keynes ra i, mi quan h ca tit kim v u t l trng tm ca cuc tranh lun. S phn bit u t v tit kim l tin nghim hay hu nghim, k hoch hay thc t? Tit kim v u t l ng nht hay l iu kin cn bng? V lm th no tit kim chuyn thnh u t lm tng sn lng l nhng vn ht sc m m. John Maynard Keynes (1883-1946) Khi cn l sinh vin, Keynes kt thn vi Bohemians ngi m sau vi nm sng lp ra din n tho lun cc vn x hi v tr thc (Blommsbury Group). H kch lit ch trch quan im ca n hong Victoria thi v c bit ng vc nhng gi tr truyn thng. Khng ch ring Keynes m c nhm ny (v v phn ng gia nh ca Keynes cng l thnh vin ca nhm) b nh hng mnh m t tng ca nh trit gia Geoge Edward Moore (1873-1958), nht l cc t tng v o c. Moore tp trung vo phn tch xung quanh nhng khi nim v th no l lng tt (goodness) v liu n c nh l mt c tnh t nhin nh nhiu nh trit hc thi ng tho lun. Moore cho rng khi nim v lng tt ca con ngi khng c nh ngha r trong iu kin phi o c, m lng tt tht ra l khng th nh ngha, khng th phn tch v l mt th hin tnh bn thn thit no v mt s nh gi cao v mt thm m. Trit l ny dn n s nghi ng s t li c nhn c th dn n hiu qu tng th ca cc nh kinh t hc c in.

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Keynes cng chng kin trn vn cuc i suy thoi M t 1929 n 1932 v Anh t 1921 n chin tranh th gii th hai bng n8. Mt thi gian di c bng chng thc nghim lm lung lay nhng tin on m trng phi c in a ra. Nn kinh t lm vo tnh trng khng hong, tht nghip cao v khng c mt du hiu no cho thy c kh nng t iu chnh tr v trng thi thnh vng nh ban u. Bi cnh ny cng y ln nh im nhu cu lm sao gii thch thc t nghch l v hn ht l gii quyt n nh th no mt cch cp thit. Cc l thuyt c in ang ng trn b vc trc s kin ca cuc i suy thoi ang din ra m khng th l gii th cng l lc Keynes xut bn quyn sch kinh in vo nm 1936, L thuyt Tng qut (Gerneral Theory). ng xy dng m hnh v m vi nhng bin tng qut xc nh. Keynes cng ging nh cc nh kinh t trc ng, ng dng m hnh di dng ng cung v ng cu ca Marshall, song cung v cu ca Keynes c nh ngha l tng (aggregate) ch khng phi mt loi hng ho ring bit nh nguyn tc ca l thuyt ca Marshall. l im mu cht lm l thuyt ca Keynes hng n mt phn tch v m hon ton mi. Trong phn tch cn bng ca Marshall bin s iu chnh l gi (ch khng phi l lng), bi v theo Marshall tng sn lng ca nh sn xut khi nhu cu tng th phi cn c thi gian mua thm my mc, iu chnh k hoch do vy gi l bin s thay i trc. Nhng theo Keynes, iu ny ng nh khng xy ra hoc khng hon ho trong mi kha cnh ca tng th nn kinh t. Gi ca vn v lao ng l iu chnh rt chm nhng cc bin v lng nh tiu dng, u t l linh hot v iu chnh nhanh chng. V th to ra cn bng tng th th s thay i trong tng sn lng ch khng phi l mc gi. Keynes loi gi c ra khi m hnh v xem nh l mt bin ngoi sinh (Friedman 1997). Keynes to c cch mng trong l thuyt v m bi cc im sau: Phn bit r rng ba th trng v mi quan h cn bng gia chng: hng ho, tin t v lao ng.

8 Giai on 1929 1932 GDP ca M gim 1/3 v t l tht nghip tng t 3.2% ln 25.2%. Nhiu nm sau cho n khi chin tranh th gii th hai bng n M vn cn c t l tht nghip cao. Anh cng vy, tnh trng suy thoi dai dn hn, suy thoi xy ra t nm 1921, t l tht nghip bnh qun t cho n chin tranh th gii th hai l 10%.

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S dng iu kin cn bng ca th trng hng ho chi mi quan h di chuyn t tit kim sang u t v dn n tng sn lng. S dng iu kin cn bng trn hai th trng hng ho v ti chnh ch ra nhiu yu t cc ng n li sut9 v sn lng.

Cch thc phn tch ca Keynes cng cho thy r s dch chuyn t phn tch vi m sang v m. y l im cho thy Keynes b nh hng mnh m t trit l ca Moore. T tr i, l thuyt ca Keynes lm mt cuc cch mng trong l thuyt phn tch v m cng nh cc chnh sch ca nhiu nc phng Ty, c bit l Anh v M. D lun phi sa i, tinh lc hoc ph phn v c s ph bng nhng l thuyt ca Keynes vn l nn tng ca kinh t v m hin i ngy nay. L thuyt v nhng ngh chnh sch m Keynes a ra c n nhn v gn nh l thng tr t nhng nm 1940 n 1970. Nhiu nh kinh kinh t hc v cc nh lch s nhn nhn Keynes nh l ngi t nn mng cho nhng ng thun sau chin tranh th gii th hai. l nhng ng thun v mi quan h ng n v cn phi c gia nh nc v nn kinh t v l nhng lun c khng th thiu v vai tr can thip ca chnh ph. Thi hong kim ca l thuyt Keynes cng l thi m h thng kinh t chnh tr ni ln vi tn gi l ch ngha t bn. Nhiu tn gi mi c xut hin nh ch ngha t bn phc li (welfare capitalism), nh nc t bn (state capitalism), c quyn t bn (monopoly capitalism). Keynes ch trch mnh m i vi trng phi c in10 v c hai pha cung v cu. V pha tng cung, ng khng phn i l thuyt c in v pha cu ca lao ng (ngha l mc tiu ca doanh nghip l ti a ho li nhun v s dng s lng lao ng sao cho nng sut bin ca lao ng bng vi sut tin lng thc). Nhng li phn i kch lit v s linh hot ca tin lng. ng tranh lun rng, cho d l mt c sc ngu nhin, hay cc c sc danh ngha no th t n phi tc ng ln cc bin s thc bi v tin lng

Cng nh Wicksell, Keynes cho rng c hai li sut l li sut tin t v li sut vn. Nhng Keynes khng gi l li sut vn m gi l hiu sut bin ca vn (mariginal efficiency of capital). Cng lu rng ba khi nim mi m Keynes ng gp cho l thuyt kinh t v m l: xu hng tiu dng bin (mariginal propensity to consume), mariginal efficiency of capital v liquidity preference.10

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Trng phi c in theo theo cch dng t ca Keynes l bao gm tt cc cc nh kinh t c in v tn c in. T Smith, Ricardo n Marshall, Pigou (Rober xxxx)

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l khng linh hot. Tnh cng nht (rigidity11) ca tin lng danh ngha l do cng nhn v cng on lun chng i ct gim lng (danh ngha) nht l trong giai on c tht nghip cao. Cng nhn lao ng khng phn ng vi tin lng thc m ng hn l h ch phn ng trn tin lng danh ngha. Hin tng ny Keynes gi l o gic tin t (money illusion). Nu tht nghip xy ra, theo Keynes th l nguyn nhn ca s suy gim tng cu hoc l nhng chu k kinh doanh. V th ko li trng thi ton dng lao ng Keynes ngh phi b p bng chnh sch ti kho. Chnh sch tin t cng c th c s dng nh l mt cng c h tr cho chnh sch ti kho v nhn chung n khng to ra s cn bng cho nn kinh t. V pha tng cu, Keynes cng c nhng ch trch i vi trng phi c in. ng nhn mnh rng, ngay c khi l c s linh hot trong sut tin lng v mc gi nh l trng phi c in lp lun th nn kinh t cng c th b kt ti mt mc sn lng di sn lng ton dng v c ch t iu chnh m trung phi c in tin tng khng vn hnh c. C hai l do m ng bo v thnh cng lp lun ny. Th nht l trong tnh hung m hm cu tin t hon ton nhy i vi li sut (hay cn gi l by thanh khon liquidity trap) v th hai l hm chi tiu u t khng nhy cm vi li sut. Trong nhng tnh hung nh vy nu c s suy gim ca pha cu, chi tiu t nh chng hn, s lm thng d cung nn mc gi gim. ng l ra, theo trng phi c in, th li sut phi gim xung u t tng tr li v ko tng cu v trng thi cn bng. Nhng v cu tin t co dn hon ton i vi li sut hoc u t khng nhy cm (vi li sut) nn tng cu vn khng thay i g (tc l vn nm di sn lng tim nng) trong khi gi gim. Keynes ngh rng, trong cc trng hp ny th chnh ph nn can thip bng chnh sch ti kho (gim thu hoc tng chi tiu) phc hi tng cu. Ngoi vic phn bc tnh t iu chnh v trng thi cn bng ca trng phi c in nh trn th Keynes l ngi m u trong vic thch thc v l thuyt s lng tin kinh in. Cc nh kinh t trong trng phi c in (v sau ny l tn c in) cho rng vic nm gi tin ca dn chng l nhm mc ch duy nht cho nhu cu giao dch, v v thNhiu ngi theo trng phi ca Keynes nhng phn i gi nh tin lng cng nht ny, nhm ny gi l Neo-Keynesian economics. Neo- Keynesian economics l kt hp gia cm t Neoclassical v Keynesian. Axel Leijohufvud l mt i din u tin ngh nn phn tch vi m ca Keynes trn nn tng vi m.11

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mc nm gi tin nhiu hay t s quan h cng chiu vi thu nhp ca h. Keynes th khng ngh nh vy, ng cho rng dn chng khng phi ch nm tin cho mc ch giao dch (hoc d phng) m h cn c ng c nm tin u c vo th trng tri phiu. Vic nm gi tin mt v tri phiu c tnh thay th nhau, khi m li sut cao th gi tri phiu s thp v ngi dn thch nm gi tri phiu hn, v ngc li trong trng hp li sut thp. V vi lp lun ny th mt ln na Keynes cng chng minh c s khng cn thit ca chnh sch tin t trong trng hp ca by thanh khon. Mt nm sau khi xut bn quyn L thuyt Tng qut, lp lun v tnh cng nht ca mc gi v tin lng ca Keynes c John Hick (1937) pht trin thnh m hnh IS-LM m sau ny c Paul A. Semuelson (1948) v Alvin Hansen (1949, 1953) pht trin v ph bin rng ri trong cc sch gio khoa v kinh t v to ra nh hng mnh m. Franco Modigliani, Friedman tip tc c nhng ng gp tch cc cho Keynes v hnh vi tiu dng12, James Tobin, Dale Jorgenson lm sng t thm v u t, li sut v cung tin. Mundell Fleming m rng m hnh IS-LM cho nn kinh t m. Trong nhng nm 1960, tt c cc tranh lun v phn tch u tp trung ngn hn, phn tch di hn rt him khi bn n ngay c cc lp sau i hc. Phn ln cc sch l thuyt kinh t v m khng tho lun mi quan h gia sn lng v lm pht, vai tr ca chnh sch tin t khng coi trng, ch tp trung nhn mnh n vai tr ca chnh sch ti kho (DeLong 2002). Trc khi bt u phn tch tip hai dng t tng r nhnh l C in Mi v Keynes Mi chng ta nhc li s bt ng cn bn ca Keynes v cc nh kinh t c in trong l thuyt tin t v chu k kinh doanh. Cc nh kinh t c in cho rng s giao ng trong sn lng s nhanh chng quay v cn bng. V tin t l trung lp v ch c nh hng ln mc gi ch khng nh hng trn lng. V th nn kinh t ch c chu k kinh doanhTrong L thuyt Tng qut, Keynes cho rng tiu dng l mt hm s ca thu nhp thc v tit kim ca h gia nh s tng ln khi thu nhp tng ln. Nm 1946 Simon Kuznet c lng thc nghim trn dy s liu tiu dng v tit kim t 1869 1938 cho thy khng c quan h nh l thuyt ca Keynes. Kt qu ca Kuznet cho thy tit kim khng thay i trong khi thu nhp ca h gia nh tng ln. Sau nghin cu thc nghim ca Brady v Friedman cng cho kt qu tng t. Ando v Modigliani xy dng l thuyt gi l Gi thuyt vng i (Life Cycle Hypothesis) gii thch s mu thun ca hm s tiu dng ngn v di hn. c lng ca h cho thy trong ngn hn hm s tiu dng vn ph hp vi l thuyt ca Keynes. Gi thuyt v thu nhp thng xuyn (Permanent Income Hypothesis) ca Friedman cng c kt lun tng t.12

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v mc gi ch khng c chu k kinh doanh v nhn dng v sn lng. Trng phi Keynes th cho rng, s trung lp ca tin ch c trong di hn ch trong ngn hn th cung tin tng mc gi s khng tng theo mt t l, v do vy cung tin thc s nh hng ln mc nhn dng v sn lng. S bt ng vn cn tip din v cc nh kinh t tip theo bo v v pht trin thnh hai trung phi kinh t gi l: C in Mi v Keynes Mi. C in Mi Tht ra Keynes thnh cng trong gii thch nn kinh t gp phi suy thoi ko di v ngh ng ng l chnh ph phi can thip. Tuy nhin nhiu gi nh qu trn (cng nh v s gi nh qu trn ca cc nh kinh t hc khc!) ca ng cng l ch cc nh kinh t k tha trng phi C in C in Mi tn cng. Keynes gi nh sut tin lng danh ngha cng nht v cho rng l mt bin ngoi sinh khng c gii thch ca m hnh l qu xa so vi thc t. N phi c gii thch, c th trong ngn hn tin lng l cng nht nhng n s thay i trong trung v di hn. iu ny ng rng cng c th nn kinh t s t iu chnh nh l cc nh kinh t c in suy lun, nh s iu chnh c th chm. Nhng nh kinh t trong trng phi C in Mi cng t nghi vn xc ng rng: liu phn tch chu k kinh doanh trong gi nh xut tin lng cng nht (ngha l ngn hn) l c tho ng khng? Thay v n phi c phn tch trong di hn khi m cc th trng u c s cn bng ng thi? Hoc l, phn tch ca Keynes l phn tch tnh (static), song trong thc t nu cc c nhn l ra quyt nh hp l th cc tp hp thng tin trong qu kh ln nhng d on trong tng lai nht nh phi c tc dng no . C l s kin ng cong Phillips l mt ct mc quan trng to nn mt khng kh st li l thuyt ca Keynes (v nhng ngi theo tng ca ng). ng cong Phillips l tn gi quen thuc c mt trong hu ht cc sch gio khoa v kinh t, l tn ca nh kinh t - ngi m vo nm 1958 c mt nghin cu thc nghim ni ting cho thy mi quan h nghch bin v n nh gia sut tng ca sut tin lng danh ngha v t l tht nghip Anh. Sau nm 1960, cng trn nim ny, Samuelson v Solow phn tch cho M cng nhn ra t l lm pht v t l tht nghip c s nh i. Hai kt qu ny ng h mnh m cho l thuyt ca Keynes. Tuy nhin, trong thp nin 60 l thuyt

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ca Keynes i din vi s kin khng gii thch c, l va c tht nghip cao v va c lm pht cao (gi l stagflation). Sau ny, Friedman v Phelps b sung lm pht d on vo m hnh ca Keynes v thng th. S liu trong thp nin 70 ng h cho lp lun ca Friedman v Phepls, ng Phillips truyn thng hon ton sp (xem hnh 1). Khi nht n l thuyt C in Mi th Lucas la ngi thng xem li mt i din tiu biu, cn Friedman l i din cho trng phi trng tin (monetarism). C hai u c nhng tranh lun bt ng mt cch thu o vi nhng ngi ng h hc thuyt Keynes. Nhng nh kinh t hc khc cng c xem thuc trng phi C in Mi l Thomas J. Sargent, Robert J. Barro, Neil Wallace, Edward C. Prescott, Finn Kydland, Robert E. Hall, Micheal Woodford, Paul M. Romer. Nancy L. Stokey. Milton Friedman (1912 -) c th xem l ngi ngi u tin tn cng l thuyt Keynes mt cch xc ng v lm hi sinh tr li nhng nim c in. Bi vit Phng php lun ca kinh t hc thc chng (1953) ca Friedman cho thy, li mt ln na, cc quan im kinh t thng c hnh bng ca quan im trit hc no m nh kinh t tn th. Nhng g m Friedman lp lun trong bi vit va nu cho thy ng nh hng mnh t t tng ca nh trit hc Karl Popper (Roger 2002). Friedman vit ch c nhng bng chng thc t mi cho chng ta phn bit c ng hay sai, tt hn, th chp nhn hoc l bc bnhng gi thuyt ch c gi tr khi chng c kim nghim thch ng thng qua so snh nhng tin on ca n vi nhng g xy ra. Phi t b nhng gi nh nu n a n nhng tin on mu thun (m thng xuyn hoc lun lun c nhng tin on khc nhau khi c gi nh thay th); n chp nhn khi c nhng tin on khng mu thun (Friedman 1953, tr 8-9). Lp lun ny khng khc g my so vi trit l phn nghim (falsificationist) ca Popper 13. Popper cho rng mt l thuyt c gi l khoa hc khi ta c th c nhiu quan st (observations) ph hp (fit) vi lNguyn c Hip (2004) c mt bi Trit l Khoa hc Hin i rt hay, ng phn tch nhng trit l khc nhau v trit hc khoa hc t thi Khai sng n nay. Theo , phng php cn bn nht l thc nghim qui np (induction), k n l ch ngha thc chng logic (Logical positivism). Trit l phn nghim ca Popper l mt pht trin cao hn v kh cc oan so vi thc chng logic. Ct li ca thc chng lgch l ch chp nhn nhng g gi l khoa hc khi c th quan st hay o c, v do c th kim chng. Cn i vi trit l phn nghim th i hi thm n phi c c hi chng t n sai v phi c nhng tin on gan d, to bo.13

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thuyt t ra. Song iu quan trng l thuyt phi cho php ta c th tm d kin (data) chng t l n sai. L thuyt ch tht s l khoa hc khi n liu lnh, to bo, "m ca" cho nhiu c hi kim chng, cha nhiu thng tin vi bng chng c th phn bin (Thip 2004). Trong khi , l thuyt ca Keynes v nhng g ng lm cho thy cha ng nn tng ca ch ngha thc chng logic (logical positivism). Trong cc t tng trit hc th trit l phn nghim l mt trong nhng lp lun da trn thc chng nhng yu cu cao hn v thm ch qu kht nghit v th no l mt l thuyt tht s l khoa hc. Vi thi ca Pooper (v tt nhin l ca Friedman) th l thuyt phn nghim c nh hng mnh m khng nhng trong trit hc m cc lnh vc khoa hc, nht l trong vai tr chng li siu hnh v ngu khoa hc (pseudo-science). Chnh iu ny cng ng gia Keynes v Friedman trong chng mc no c hai nhn quan khc nhau v trit hc khoa hc (philosophy of science). iu ny c th khng c nhiu ngi quan tm bng cc l thuyt kinh t m h xy dng, nhng chnh n cng n v ng c m Friedman xt li l thuyt ca Keynes. Trn l thuyt kinh t v m tng qut, c 4 yu t m Friedman ng gp (DeLong 2002): Theo Friedman th nng lc nh nc trong qun l nn kinh t thng th khng chn chn, chm tr, v nhng chnh sch thng c tc dng rt t nht l trong vic ko nn kinh t ra khi suy thoi v tht nghip cao. Ngc vi Keynes, ng ch trch vic cc m hnh chun ang nh gi qu cao vai tr ca chnh sch ti kho m xem nh vai tr ca chnh sch tin t. Theo ng th nn ngc li. ng gp quan trng hn l vic o lng cung tin cng nh s vn hnh ca chnh sch tin t trong thc t nh th no. ng gp cui cng l khi nim t l tht nghip t nhin (natural rate of unemployement). By gi chng ta tr li nhng g m Friedman thch thc Keynes trong m hnh tng qut. Vn da trn nn tng tng qut ca trng phi c in v k c ca Keynes,

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Friedman bt u c nhng hiu chnh quan trng. Th nht v pha tng cung, tc l th trng lao ng14, cc ch doanh nghip c thng tin v gi c nhiu hn v h ch cn quan st mt s t sn phm (chng hn nh sn phm m h ang kinh doanh, cc nghin liu u vo ), ngc li, cng nhn phi i din vi tp hp rt nhiu sn phm m h tiu dng v cng khng c thi gi theo di gi c nhanh chng. V th i vi ch doanh nghip, tc l cu lao ng, th h s phn ng vi tin lng thc (real wage) trong khi th cng nhn, tc l pha cung, phn ng vi mc tin lng thc k vng (v h ch c mc gi k vng). y l gi nh k vng thch nghi (adaptive expectation) ni ting ca Friedman thnh hnh trong nhng nm 1960 -1970. V pha tng cu, Friedman th cho rng hm cu tin t rt t nhy cm vi li sut. C th hn, thay v Keynes ch xem l do dn chng mun nm gia tin th Friedman li xem tin nh l mt sn phm lu bn cho h gia nh ln x nghip. Chnh v l do m Kyenes cho rng dn chng nm gi tin v mc ch giao dch v u c nn khi nim thu nhp trong hm cu tin ca Keynes l thu nhp thc. Ngc li, thu nhp trong hm cu tin ca Friedman l thu nhp thng xuyn, ngoi ra cn nh hng ca chnh lch gia mc sinh li li sut hin hnh trn phiu n d on, li sut c phn hin hnh, t l lm pht d on vi li sut d on trn tin (bao gm li sut thc tr ca ngn hng v nhng dch v m h cung cp)15. Tuy nhin, mc chnh lch ny t khi bin ng v p lc cnh tranh nn cc ngn hng cng thay i li sut trn tin khi m cc bin s kia thay i. Phn tch ny ca Friedman dn n hai kt lun quan trng mu thun vi Keynes: th nht l cc chnh sch v ti kho hu nh khng lm thay i tng cu; th hai khi tin t xc nh tng cu. V th s thay i trong cung tin c tc dng i vi nhn dng v sn lng trong ngn hn v c s chnh lch gia gi thc t v gi k vng nhng trong di hn c th trng lao ng v sn phm u tr v trng thi cn bng. V nh vy chu k kinh doanh xy ra l do s chnh lch gia mc gi m cng nhn k vng so vi mc gi thc t.

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V trong ngn hn cng ngh l khng thay i, hm tng cung n gin ch l mt hm s v lao ng. Keynes gi l li sut r (explicit interest) v li sut ngm (implicit interest).

15

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Ngi k tc Friedman trong tn c in l Robert E. Lucas (1937-). ng c cng trong vic ci thin nhng nhc im m Friedman khng gii thch c. Vic m cng nhn c thng tin v gi c tr hn ch doanh nghip nh Friedman ngh l khng c g sai, song cng nhn khng th ngu lu v cc ngun thng tin v mc gi thay i thng xuyn c cp nht bng phng tin truyn thng i chng. V nh th th khng th no l gii c chu k kinh doanh ko di n 3-4 nm trong nhng nm sau chin tranh th gii th hai. ng gp ca Lucas i vi Friedman l phng din d on. Thay v dng gi nh d on thch nghi th Lucas cho rng cng nhn d on hp l (rational expectation)16. Ci gi l hp l y, ch khng phi l thch nghi, l da trn mt gi nh rng ch th kinh t hnh thnh s d on v mt bin s no u cn c trn tt c cc thng tin thch hp v sn c. Thnh thong vn c nhng d on sai lm nhng s sai lm khng c tnh h thng, ngha l ngu nhin. Lucas cho rng khng nhng ch ring cng nhn thit thng tin v gi c m ch doanh nghip cng trong tnh trng tng t. V th c hai u phi a ra nhng d on v gi c cho mc tiu ca mnh. Vi gi thuyt d on hp l v s l ton hc th Lucas cng dn n cng mt kt lun vi Friedman, nhng cho thy qu trnh iu chnh s nhanh hn so vi m hnh ca Friedman. Ring v vai tr ca chnh sch tin t, cng vi gi nh k vng hp l, Thomas Sargent v Wallace li c mt ng gp hi khc so vi nhn nh ca Friedman nhng li cng dng t tng ca Tn c in. Kt lun ca Friedman cho thy s thay i cung tin lm nh hng n sn lung v vic lm trong ngn hn, nhng cu hi t ra l liu c th dng chnh sch tin t nh l mt bin php ko cc th trng v trng thi cn bng khi c giao ng hay khng? Cu tr li l khng nu ngi dn cng bit hoc on c vic tng cung tin ca ngn hng trung ng. Cung tin ch tc ng n sn lng v vic lm khi n xy ra bt ng. Kt lun ny c gi l mnh PIP17.

Khi nim d on hp l tht ra c Jonh Muth a ra vo nm 1961 nhng n tht s pht trin ng dng phn tch v m l do Lucas.17

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Mnh PIP ngy nay vn l mt tranh ci. Nghin cu thc nghim ca Barro (1977) cho thy ph hp vi PIP, nhng nghin cu ca Minskin (1982) v Gordon (1982) li c kt qu khng ph hp vi mnh PIP

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Nh th li mt ln na cng khng gii thch tho ng nhng chu k kinh doanh ko di 3 hay bn nm v s cp nht thng tin khng th qu lu nh vy. Tip tc lp y nhng khe h ny, mt s nh kinh t m ch soi l Finn E.kydland, Eaward Prescott, Rober G.King, Barro, John Long v Charles I.Plosser, pht trin m hnh gi l chu k kinh doanh thc (real business cylce). L thuyt chu k kinh doanh thc pht trin vo u nhng nm 1980. im chnh ca ln ny l h pht trin mt m hnh hm sn xut ton din hn thay v ch c mt yu t sn xut l lao ng (do vy cc v trn ch tm cch sa sai trong th trung lao ng m thi!) th t bn v k thut l hai yu t gp phn quyt nh sn lng. Nh vy, nu trong tnh trng k thut trung bnh th mi th trng u cn bng, nhng nu k thut gp phi cc c sc thun li hoc khng thun li th sn lng t nhin s tng hoc gim theo tng ng18. Vic tng hay gim theo ny cng ng thi vi tin lng thc, nhn dng tng hay gim. Trong m hnh h xy dng, vic nhn dng tng hay gim phn nh mt phn do tin lng thc thay i v mt phn ph thuc vo hm tho dng ca cng nhn trong la chn thay th gi tiu dng hay l hng nhn. l cch m h l gii s giao ng trong cc chu k kinh t. L thuyt chu k kinh doanh thc khng quan tm nhiu n chnh sch tin t, h xem cung tin l ngoi sinh. Vic m rng hay thu hp cung tin l th ng phn ng theo chu k thay i ca nhu cu ca tn dng. Keynes Mi Cng b ch trch bao nhiu th cng l ng lc mnh m cc nh kinh t theo truyn thng ca Keynes mi gia l thuyt ca Keynes thm sc bn by nhiu. H gim bt gi nh tin lng cng nht ca Keynes bng nhng l gii tho ng hn. Tin lng khng linh hot theo h l c v nguyn nhn ch yu bt ngun t cc nhn t nh ch (institutional factor), chng hn nh cnh tranh c quyn (monopolistic competition), chi ph thc n (menu cost), kh c di hn (lengthy contract), l thuyt tin lng hiu qu (efficiency wage theory), gi n nh (markup pricing), chin lc

18 Khi nim thc trong tn gi chu k kinh doanh thc c ngun gc t im ny. Nhng nm gn y l thuyt chu k kinh doanh thc c hiu ng ngha nh l trng phi C in Mi. Gn y, Jordi Gal v Pau Rabanal (2004) c mt nghin cu thc nghim dy s liu 1948 - 2002 cho thy mi quan h gia giao ng sn lng v cng ngh rt gii hn.

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marketing (marketing stragegy) Linh hn trong cc l thuyt trong trng phi Keynes mi l phn tch trn nn tng kinh t vi m (mirco-foundations) cho thy trong nhiu trng hp tt trn bnh din vi m c th phng hi n kinh t v m. Bn im chnh m nhng ngi trong trung phi Keynes Mi ch trch trng phi Tn C in l: th nht trong thc t c s phn phi thng tin khng ng u; th hai gi nh mc gi linh hot tuyt i trong gi nh k vng hp l l khng r rng trong thc t; th ba, k vng hp l khng phi lc no cng c v vi mi th trng; th t l gi nh th trng u trong tnh trng cn bng nh l mt th trng cnh tranh hon ho l khng c tht m hu ht cc th trng u c c tnh l cnh tranh c quyn, n gin l chi ph hnh thnh mt doanh nghip mi cng l mt ro cng gia nhp ngnh (Roger 2002). Trng phi Keynes Mi ni ln t cui thp nin 70, nhng i din ni bt l Olivier Blanchard, Nobuhibo Kiyotaki, Alan Blinder, Stanley Fischer, Rober Hall, Lawrence Katz, Gregory Mankiw, Micheal Parkin, Joeshep Stiglitz, Lawrence Summer, John Taylor v Janet Yellen. Phn bn di chng ti s im qua ba l thuyt in hnh theo trng phi Keynes mi l kh c di hn, chi ph thc n v sut tin lng hiu qu. Fischer v sau l Taylor l hai i din ln v l thuyt xy dng trn gi nh kh c di hn19 chng minh rng chnh sch tin t h thng cng c tc dng n sn lng ch khng phi nh nhng g m nh PIP ca cc nh kinh t tn c in pht biu bn trn. Fischer cho rng, thc ra khi cng nhn k hp ng vi ch doanh nghip th h s thng lng mc tin lng v n c hiu lc trong mt khong thi gian no . Sau khi ht khong thi gian th tin lng li tip tc c tho lun. Vic tho lun v ra quyt nh ca cc tc nhn kinh t ny khng phi cng mt lc v u ging nhau nn khng th tc ng nh l mt hp lc cng chiu n chu k kinh doanh. Gi s rng c hai thng lung giai on u tin u t c mc lng cn bng. Tin lng thng lng cho giai on k tip ca cng nhn phi tng ng bng sut tng ca gi. Nhng cng nhn li khng c gi cho giai on k tip nn h phi dng k vng hp l d on. Vi cch lp lun ny th Fischer chng minh c vi khi khCc tn gi khc ca m hnh ny l tht bi phi hp (coordiantion failures) v mc gi chng cho (staggered prices)19

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c c hiu lc trong hai thi k th chnh sch tin t c h thng c tc dng i vi sn lng. Mt lp lun tip theo cng ng h cho Keynes v vic cng nht trong cc bin s danh ngha l chi ph thc n. L thuyt ny lp lun rng khng nhng tin lng l cng nht m gi sn phm cng vy. Bi v vic iu chnh gi cn tu thuc vo chi ph c hi. Nu chi ph c hi ca vic iu chnh gi l thp hn chi ph iu chnh gi (hay cn gi l chi ph thc n) th khng c ng c cc x nghip iu chnh, v ngc li. Nu trong nn kinh t c a s cc doanh nghip cnh tranh c quyn th hnh vi t li ny s gay tn hi n tng th nn kinh t. Bi v, chng hn cung tin gim lm gim tng cu danh ngha, ng l ra mc gi cng phi c iu chnh nhng v chi ph iu chnh c th cao hn chi ph c hi ca vic iu chnh th doanh nghip s gim sn lng tip tc ti a ho li nhun. Tt c cc doanh nghip u hnh x nh vy th s lm tng sn lng gim v dn n nhn dng cng gim. Mt ng gp khng km phn quan trng khc trong dng t tng ca Keynes mi l l thuyt sut tin lng hiu qu. tng cn bn ca l thuyt ny cho rng vic trong nn kinh t lun c tht nghip t nguyn l hon ton hp l. Bi v cc x nghip c ng c tr mc lng cao hn mc lng cn bng trn th trng lao ng, gi l tin lng hiu qu. S d h tr cao hn l v khch l cng nhn trnh sao nhn trong vic lm20. Tin lng hiu qu m x nghip tr cho cng nhn c xc nh bi s c gng hay hiu lc ca cng nhn ch khng phi t cu lao ng. V thng l cc x nghip s khng thay i tin lng hiu lc ny ngay khi c cu lao ng gim, x

C hai trung hp dn n sao nhn vic lm ca cng nhn. Th nht l vic gim st, nu gim st khng chc ch th cng nhn s chnh mng cng vic. Nhng chi ph gim st thng la tn km. Th hai l nu x nghip tr lng ng bng mc lng cn bng th cng nhn b sa thi h c th tm mt vic lm tng t vi mc lng tong t ngay, ngha l khng c p lc. Nhng nu tr cao hn mc lng cn bng th h ch tm lm vic tt hn v kh nng tm mt mc lng nh vy l kh (Stiglitz v Shapiro 1984). Ngoi ra, c nhiu cch gii thch khc nhau nhng ng h cho lp lun rng x nghip thng tr lng cho cng nhn cao hn mc lng cn bng cnh tranh, nh Weiss (1980) cho rng s d nh vy v thng cng nhn bit c nng sut lao ng ca mnh hn l ch x nghip v trung bnh th nhng ngi ny u c lin h dng gia nng sut lao ng ca h vi tin lng. Salop (1979) th cho rng tr lng cng nhn cao th s gim c t l thay th cng nhn khi thi vic, v do gim chi ph tuyn dng cng nh o to. Akerlof (1982) th lp lun tru tng hn, cho rng vic tr lng cho cng nhn chnh l tng vt (partial gift exchange) ca x nghip i vi cng nhn i li cng nhn cng tng vt cho x nghip mt mc nng sut cao hn. V chnh mi quan h qua li ny s gip cn bng tin lng gia hai bn.

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nghip s chn bin php ct gim cng nhn hn l gim tin lng. S d iu ny xy ra l v khi x nghip gim tin lng hiu lc s lm chi ph tin lng trn mi n v hiu lc s tng v dn n chi ph tin lng trn mi n v sn phm s tng21. Lp lun va ri gii thch ti sao c s cng nht trong tin lng thc, tuy vy y cng l im b ch trch. Cho d tin lng thc c th l cng nht nhng iu khng l gii c nhng tnh hung c bit. Chng hn cung tin gim nhng cng lc t l gim ca gi cng bng vi t l gim ca tin lung danh ngha (ngha l vn m bo tin lng thc khng i) th vn khng c gim sn lng v nhn dng. Do vy, l thuyt tin lng hiu qu thng kt hp vi l thuyt chi ph thc n hoc kh c di hn trnh trng hp va xy ra trn. Xu hng ca l thuyt kinh t v m? Ngoi tr nhng nh kinh t xy dng l thuyt chu k kinh doanh thc, th trng lao ng dng nh l mt mnh t truyn thng m cc nh kinh t lm bn p tn cng ln nhau hay sa sai v pht trin. Nhng nhiu bng chng thc nghim v tin lng v mi quan h ca n vi sn lng th khng t ra ng h cc m hnh l thuyt , n ch thun logic. Mi quan h ca s giao ng ngc chu k ca sut tin lng thc m cc l thuyt, gm Keynesian, Friedman, Lucas hay Fischer lp lun u khng c s liu lch s ng h (xem hnh 1) (Katz 1986) hay nghin cu thc nghim v s chnh lch ca sut tin lng hiu lc cng khng c bng chng thc nghim gii thch tho ng (Hall 1980). V l thuyt chu k kinh doanh thc, hai im chnh to nn kt qu gii thch ca h c nh hng trong l thuyt kinh t v m, nh trnh by bn trn, l (1) phn tch hu ch bin gia hng nhn v lm vic22 v (2) s thay i cng ngh. Tuy nhin thc t cho thy c rt t lao ng mun thay i cng vic ca mnh nh i vi vic hng nhn d cho rng, hoc k vng rng trong tng lai s c tin lng sng sa hn. Cc cng nhn thng mun lm vic lin tc. H tht nghip bi v h mt vic, ch n gin

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Trong thc t vic kim nghim li l thuyt tin lng thc t bng kinh t lng khng cho thy c kt qu r rng (Katz 1986). S chnh lch trong mc tin lng c th n t cc nguyn nhn khc na. 22 Thut ng gi s s nh i ny l intertemporal substitution of labor

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nh vy. Cn i vi cng ngh, m c th l nng sut trong nn kinh t s thng trm trong tng giai on, chng hn nh trong lc suy thoi th nng lc ca cc nh my s gim i v nhng nh u t s rt vn. Th nhng, l thuyt ny li khng quan tm n mt kha cnh khc l cc nh u t cng hon ton c th t duy hp l cho mt giai on tng trng mi v cng li l mt c hi cho u t mi. S giao ng trong u t phi c l gii tho ng hn. C l, cng l mt khong trng cc nh kinh t hc tip tc ng gp gii thch chu k kinh doanh thuyt phc hn. DeLong (2002) rt thch th im ny! Bn trn l nhng ht sn (chnh?) trong tng l thuyt c xy dng. Cn v bc tranh chung th s bt ng gia C in Mi v Keynes Mi vn cha gii quyt tho ng v mi bn c mt sc thuyt phc hp l ring. V c bn h vn thng nht vi nhau v c ch ca nn kinh t trong ngn hn v di hn, song th no l ngn hn v di hn nht l v chnh sch l lun c s bt ng. Cuc tranh lun vn l tin lng v gi c thay i nh th no, mau hay lu? V phng php lun, nhng nh kinh t hc trong trng phi C in Mi thng c nhng ng gp ca mnh da trn nn tng ca cn bng ton phn ca Marshall, h cng cho rng gi c l phn nh y tn hiu th trng v lun cn bng. Ngc li, nhng ngi trong trng phi Keynes th d trn nn tng ca kinh t vi m v cho thy rng th trng l khng r rng (unclear), s kt dnh ca gi c v tin lng l nguyn nhn gii thch ti sao c tht nghip t nguyn v chnh sch tin t v ti kho c tc dng trong nn kinh t. Nhng mt xu hng quan trng l c hai u tp trung phn tch v m trn nn tng ca kinh t vi m (microfoundation). Chng hn nh l thuyt chu k kinh doanh ca Lucas gii thch v s giao ng ca s d ca Solow (Solow residual) kt lun mt quan h cng chiu vi sn lng. Hoc cc nh kinh t trong l thuyt Keynes Mi th gii thch cc hnh vi vi m chng minh cho s kt dnh ca tin lng v mc gi. Tt c u da trn iu kin ti a ho li ch ca cc ch th trong nn kinh t: doanh nghip, cng nhn, ngi tiu dng.

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Ti liu tham kho Alvarez, Fernando v Robert E. Lucas, 2001, Interest Rate and Inflation, Federal Reserve Bank of Minneapolis, Working Paper 609. Blanchard, Olivier J., 2000, What do We Know about The Macroeconomics that Fisher and Wicksell did not?, NBER WP 7550. Blanchard, Olivier J., 2000, Marcroeconomic, 2nd edition (Prentice-Hall, 2000) Blanchard, Olivier J. v Jordi Gal, 2004, A suggested Modification to the New Keynesian Model Mimeo. Cornwall, John and Wendy Cornwall, 2005, Power and Institutions in Macroeconomics Theory, CEPP Working Paper No. 02/05 [University of Cambrige] DeLong J.Bradford, 2002, Macroeconomics, (Burr Ridge, IL: McGraw-Hill Higher Education: 0072328487). Mt vi chng c th xem ti: http://www.j-bradforddelong.net/macro_online/Index.html Ekelund, Robert B. v Robert F. Hbert, 2004, Lch s cc Hc thuyt Kinh t, Nh Xut bn Thng K [Bn dch ting Vit]. Friedman, Milton, 1976, Inflation and Unemployment, Nobel Memorial Lecture. C th xem ti: http://nobelprize.org/economics/laureates/1976/friedman-lecture.html [bng dch ting Vit ng trong sch: Cc thuyt trnh ti l trao gii thng Nobel - V khoa hc Kinh t 1969-1980, NXB Chnh tr Quc gia, 2000] Friedman, Milton, 1997, John Maynard Keynes, Federal Reserve Bank of Richmond Economic Quarterly Vol. 83/2. Gal, Jordi v Pau Rabanal, 2004, Technology Shock an Aggregate Fluctuation: How Well does the RBC Model Fit Postwar U.S. Data?, [Prepared for the 19th NBER Annual Conference on Macroeconomics] Humphrey, Thomas M., 1997, Fisher and Wicksell on The Quantity Theory, Federal Reserve Bank of Richmond Economic Quarterly Vol. 83/4. Katz, Lawrence F., 1986, Efficiency Wage Theories: A Partial Evaluation, NBER Macroeconomics Annual, Vol. 1, pp. 235-275. Cambirdge, MA : MIT Press, 1986. Kraus, Wiladimir, 2005, The Fundamental Error of Mainstream Macroeconomics, Mimeo. Laidler, David, 2001, The Role of The History of Economic Thought in Modern Macroeconomics, Ti liu trnh by ti Hi tho Ngn hng Anh quc.

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Lucas, Robert E. 1995, Monetary Neutrality, Nebel Price Lecture. C th xem ti: http://nobelprize.org/economics/laureates/1995/lucas-lecture.html [bng dch ting Vit ng trong sch: Cc thuyt trnh ti l trao gii thng Nobel - V khoa hc Kinh t 1991-1995, NXB Chnh tr Quc gia, 2000] Mankiw, N. Gregory, 1990, A Quick Refresher Course in Macroeconomics, NBER WP3256. Mankiw, N. Gregory, 2003, Macroeconomics, 5th edition (Bedford :Worth, 2003) [Bn dch ting Vit] Niggle, Christopher J. 2004, A short Course in Macroeconomics or Whatever Happened to Monetarism?, Mimeo [Prepared for submission to Review of Political Economy] Nguyn c Hip, 2004, Trit l khoa hc hin i, Thi i Mi, s 2. Xem ti: http://www.thoidai.org/ Phm Chung v Trn Vn Hng, 2002, Kinh t V m Phn tch, Nh Xut bn i hc Quc gia TP HCM. Roger Bjrnstad, 2002, The Major Dabates in Macroeconomic Thought a Historical Outline, The Essay was prepared for PhD courese. Stiglitz, Joseph E. v Bruce Greenwald, 1987, Keynesian, New-Keynesian and New Classical Economics, NBER WP 2160. Thi Kim Lan, 2004, Khai sng v Tin b - Nhn t gc trit s Ty phng, Thi i Mi, s 3. Xem ti: http://www.thoidai.org/ Woodford, Micheal, 1999, Revolution and Evolution in Twentieth Century Macroeconomics, Mimeo.

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Hnh 1: Mi quan h gia lm pht v tht nghip M trong nhng giai on khc nhau

Ngun: Lucas 1995.

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Hnh 2: Mi quan h gia nhn dng v tin lng thc (ngn hn)0.002

0.002

0.001

S thay i trong tin lng thc-300 -200 -100

0.001

0.000 0 100 200 300 400 500 600

-0.001

-0.001

-0.002

S thay i nhn dng (nghn lao ng)

Ngun:

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