L’approccio di Tobin all’equilibrio di portafoglio e nuova macroeconomia PDF

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L ’ appr occi odi Tobi nal l ’ equi l i br i odi por t af ogl i o.Unappr occi oal t er nat i v oal l at eor i adel l apol i t i ca monet ar i aèquel l oadot t at odaTobi n,checonsi der aval amonet aun’ at t i v i t à,machei nvecedi anal i zzar eun’ uni caat t i vi t àoun’ i nsi emedi at t i v i t àdadenomi nar emonet a,hapr esoi nesameuna var i et àdi at t i vi t àcheandavanodal l aval ut al egal eal capi t al efisi co.Egl i hacos t r ui t ounaser i edi model l i i ncui l avar i abi l edeci si vaèr appr esent at adalr appor t odi val ut azi one:l acosi ddet aQ di Tobi n,cheèi l r appor t ot r al aval ut azi onedi mer cat odel l ost ockdi capi t al eei l suoval or eal cost o disost i t uzi one.Nel l ’ i mpost azi onedi Tobi nqui ndisi puòut i l i zzar eancor ai l model l odi baseI SLM ancheperr appr esent ar eun’ economi aconunset t or efi nanzi ar i ocompl essoel ac ur vaLM non descr i vel ’ equi l i br i osempl i cement enel mer cat odel l amonet a,maèqui ndi i l r i sul t at odel l ’ equi l i br i o del l ’ i nt er oset t or efinanzi ar i o. Leaspet t at i v er azi onal i el anuovaec onomi acl as si ca:Leaspet t at i ver azi onal i .Ver sol amet àdegl i anni 70l aMacr oeconomi ahasubi t ounat r asf or maz i onegr azi eal l ’ i nt r oduzi oneeal l ’ i mpi ego si st emat i codelconcet t odi aspet t at i v er azi onal i .L ’ i deaf ondament al e chest aal l abasedel l ’ i pot esi diaspet t at i v er az i onal i ,èchel agent eappr endeemodel l al epr opr i easpet t at i vesul l abasedi t ut t e l ei nf or mazi oni di sponi bi l i .I l compor t ament onel l ’ acqui si zi oneenel l ’ usodel l ei nf or mazi oni sar à det t odal pr i nci pi odel l amassi mi zzazi onedel l ’ ut i l i t à;ser i sul t avant aggi osoacqui si r eunanuova i nf or mazi one,oi mpi egar ei nmodopi ùeffici ent eun’ i nf or mazi onegi àposs edut a.Isogget t il o f ar anno.Lat eor i adel l easpet t at i ver azi onal i èdi venut àc osìpopol ar enegl i anni 70per chél e r i cer chesul l ecur v edi Phi l i psconaspet t at i vehannodi most r at ochel af or mazi onedi aspet t at i ve i nflazi oni st i cheèdeci si vanel det er mi nar ei l f unzi onament odi un’ economi ai npar t i col ar el esue modal i t àdi r i spost aal l apol i t i camonet ar i aefi scal eei nol t r eper chéi l concet t or appr esent a l ’ appl i cazi oneal l af or mul azi onedel l ’ aspet t at i vedel l ’ i pot esi di compor t ament i i ndi vi dual i ot t i mi zz at e, cheer ast at apr ogr essi v ament eappl i cat aal l eat t i vi t à. Lanuovamacr oeconomi acl assi ca.Lanuov amacr oeconomi acl assi caconi ugal ’ i pot esi del l ’ as pet t at i ver az i onal i conl ’ i pot esi del t assonat ur al edi di s occupazi one.Sel easpet t at i v esono r az i onal i ,dev onor i sul t ar ei nmedi acor r et t enel l ungoper i odo;al t r i ment i c i òsi gni fi cher ebbechel a gent et r asc ur aal cunei nf or mazi oni f aci l ment er eper i bi l i .Lanuov at es i c l assi caper òsispi nseol t r e. Sec ondol anuov aec onomi acl as si c a,l apol i t i caeconomi caperquant ocondot t aconeffici enz a, nonpot ev aeser ci t ar eeffet t i si st emat i ci s ul l apr oduzi one, amenochei lgov er nonondi sponesse d’ i nf or mazi oni sul l ’ economi api ùcompl essedi quel l edel set t or epr i v at o( Phel pseFr i edman di cevanoal cont r ar i ochel apol i t i cadi st abi l i z zazi oneer aposs i bi l e) .Lapol i t i caeconomi capot ev a i nfluenz ar el adi socc upaz i onesol opr ovocandoaspet t at i veer r at ei nbaseal l ’ i pot esi del l ’ aspet t at i ve r az i onal i ,quest ier r or i dov ev anor i sul t ar ecasual i ei mpr ev edi bi l i .Nonvi er ai nf at t i al cunr appor t odi sost i t uz i onedi sponi bi l e ,nemmenonel br ev eper i odo,t r ai nfl azi oneedi s occupazi one( l acur vadi Phi l i pser aver t i c al eanchenel br ev eper i odo) .Unadel l aat t r at t i v edel l anuov amacr oeconomi a cl assi caèl acapaci t àdi abbr acc i ar eunav ast agammadi pr obl emi ent r ounquadr ocoer ent e.I l t emacent r al eedomi nant eèl ar az i onal i t ài ndi vi dual e:l ’ i pot esi del l amassi mi z zazi onedel l ’ ut i l i t à vi enequi ndi por t at aadest r emeconseguenze.Tut t oi l r est oèsubor di nat oaques t oassi oma. Ri spost eal l anuov amac r oeconomi acl assi ca.Ic oncet t i di scussi nei duepar agr afipr ecedent i sono t r oppor ecent i edèt r oppopr es t operval ut ar el el or osor t i al ungot er mi ne,ècomunquepossi bi l e f ar eunaser i edi pr eci sazi oni :èst at or i conosci ut ochef ar el ’ i pot esidi aspet t at i ver azi onal i cost i t ui s ceunost r ument ot eor i coi nest i mabi l e;l anuov amacr oeconomi ahadat oi l vi aadun cospi c uopat r i moni odi r i cer chet eor i c heedempi r i che;l adi s t i nz i onet r akey nesi ani emonet ar i s t iè di venut ai r r i l ev ant eperanal i zzar el eposi z i oni r el at i v eal l amac r oeconomi a. I l ci cl oeconomi co:i model l i mol t i pl i cat or eac cel er at or e.Lagener al Theor yhaeser ci t at oun’ enor me

i nflussosul l at eor i adel ci c l oeconomi co.Gr azi eadessasi èi ni z i at oadusar eunmodel l odi mol t i pl i cat or eaccel er at or e.Lat ensi onedi quest oappr occi oèdovut aal f at t ochei l c i cl oemer ge nat ur al ment ecomeeffet t odel l ’ i nt egr az i onedi duesempl i ci r eazi oni .L ’ accel er at or espi egaper ché, adesempi o,unacadut adelt assodi c r esci t adel c onsumopr ovochipacadut adel l i v el l o d’ i nv est i ment o.Ci òasuavol t a,t r ami t ei l mol t i pl i cat or e,f aabbassar econs umo, pr oducendouna sv ol t anel l apr oduz i one.T al eappr occi ohaor i gi ni Keynesi anemasubi sceanchel ’ i nfluenzadi Af t al i on,Cl ar keRober t son;t ut t avi aper òcomedi most r at odaSamuel son,i model l i mol t i pl i cat or e accel er at or ehannol apr opr i et àcr i t i cadi pr odur r eci cl i chesi smor zanooppur eci cl i espl osi vi e qui ndi perf arsi chequest omodel l odi v ent asseunmodel l oc ompl et odel ci cl oer anecess ar i o i nt r odur r eal t r i f at t or i ( Hi ck speresempi oadoper av aunmodel l oi ncui unpr oces soi nst abi l i edi mol t i pl i cat or eaccel er at or eoper av at r aunt et t oi mpost odal l api enacapaci t àpr odut t i v aeunl i vel l o mi ni moal di sot t odel qual el ’ i nv est i ment ononpot ev acader e) ....