虛擬貨幣市場的價格投機泡沫實證研究

北京理工大學珠海學院2020屆本科生畢業(yè)論文虛擬貨幣市場的價格投機泡沫實證研究（申優(yōu)）虛擬貨幣市場的價格投機泡沫實證研究摘要股神沃倫·巴菲特曾經(jīng)這樣評價虛擬貨幣的價值，他認為其只是一場海市蜃樓，投資者應該遠離它。下一個投資者出價的高低決定了虛擬貨幣的價格，而對于這種主觀意愿的決定極易產(chǎn)生價格投機泡沫，無數(shù)研究者運用模型實驗去尋找其中的奧秘，本文選用了五種虛擬貨幣分別是比特幣（BTC）、以太坊（ETH）、瑞波幣（XRP）、萊特幣（LTC）和達世幣（DASH）作為研究數(shù)據(jù)，并運用Phillipsetal.（2011；2015）所提出的檢驗方法SADF以及GSADF來檢測泡沫的存在與否、泡沫的產(chǎn)生與破裂時點以及其持續(xù)時長，從而對虛擬貨幣市場的價格投機泡沫進行實證研究，結果顯示五種虛擬貨幣均存在價格泡沫，且持續(xù)期較長時期為2017年，并根據(jù)虛擬貨幣市場現(xiàn)狀提出相應的建議以及本文的不足之處。關鍵詞：虛擬貨幣；價格泡沫；SADF檢驗；GSADF檢驗

SpeculativeBubbleinCryptocurrencyMarketAbstractInvestorWarrenBuffettoncedescribedthevalueofvirtualcurrenciesasamiragethatinvestorsshouldstayawayfrom.Nextthediscretionoftheinvestorsbiddeterminesthepriceofthevirtualcurrency,anddecisionsusceptibletopriceforthiskindofsubjectiveintentspeculativebubbles,manyresearchersusingmodelexperimenttofindthemystery,thisarticlechoosesthefivetypesofvirtualcurrencyareBitcoin(BTC),Ethereum(ETH),Ripple(XRP),Litecoin(LTC)andDigitalCash(DASH),astheresearchdata,andusessuchasPhillipsetal.(2011;2015)inspectionmethodSADFandGSADFtodetectwhetherthereisafoam,aswellasbubble’soccurrence,rupturetimeandendurancetimeforthevirtualcurrencymarketpricespeculationbubbleempiricalstudy.Theresultsshowthattherearepricebubblesinthesefivevirtualcurrencies,andtheperiodof2017yearsisthelongestduration.Besides,accordingtothepresentsituationofthevirtualcurrency,wemakesomecorrespondingrecommendationsandoutlinethedeficiencyofthisarticle.Keywords:Virtualcurrency；Pricebubble;SADFTest;GSADFTest

[7].4.3.3GSADFinspectionAlthoughtheSADFtest'sestimationofasinglebubbletestisimmediate,theactualassetpricechangeprocessisverycomplicated.Whentherearemultipleexplosivestructuralmutationsintheprice,thetestabilityisreduced,andthetestcanonlymeasure.Whetherthereisfoam,butthetimingoffoamgenerationandburstingcannotbedetected.Basedonthis,Phillipsetal.(2015)madecorrespondingimprovementsonthebasisofSADFtest,andgotamoregeneraltestmethod-GSADFtest.UnliketheSADFtest,thestartingpointintheGASDFtestsampleisnot0,thatis,thestartingpointandtheendpointarenotfixed,soyoucangetmoresamplesthantheSADFtest.TherecursivemethodofGSADFandSADFareexactlythesame,allarerecursiveforwardthesamplesizegetsitsstatistic,andthencomparesthisstatisticwithitscorrespondingrightcriticalvaluetotestwhethertheoriginalhypothesisisrejected.Ifthestatisticisgreaterthanitscriticalvalue,rejectingthenullhypothesisandacceptingthealternativehypothesis,thatis,thereisabubbleinitsprice,andconstructtheGSADFstatisticas: GSADFrThesampleselectionmethodofGSADFtestisshowninFigure8:Figure8GSADFsampleselectiondiagramAccordingtotheaboveanalysisandcomparison,themostobviousdifferencebetweentheGASDFtestandtheSADFtestisthattheGASDFtesthasalargernumberofsubsamplesintherollingwindowthantheSADFtest,sothecorrespondingresultswillbemoreaccurateandreliable,thismethodhasobviousadvantagesforcheckingwhetherthereisabubbleindigitalcurrency.Therefore,throughthecomparisonandanalysisoftheexistingtestmethods,thispaperfinallychosetheSADFtestandGSADFtestproposedbyPhillipsetal.(2011;2015)forresearchandanalysis.Empiricalresults5.1DescriptivestatisticalanalysisTable5.1DescriptivestatisticsoffivevirtualcurrenciesBTCETHLTCXRPDASHMeanvalue4272.118206.454852.418330.271088162.2766Median3585.120140.240039.480000.22800690.080000Maximumvalue19497.401396.420358.34003.3800001550.850Minimumvalue210.49000.4348292.6300000.0040902.060000Standarddeviation4002.243249.493360.378880.365032225.2759Skewness0.8873291.7288371.7212713.3528152.530587Kurtosis3.1526306.1295786.42091121.0942310.58912Jarque-BeraStatistics201.59891382.0161496.64323660.795287.319Firstly,thedescriptivestatisticalresultsoffivevirtualcurrenciesareanalyzed.AsforBTC,itcanbeseenfromtheabovetablethatduringtheselectionperiodoftheclosingpricedata,thepricerangeofBTCis[210.49,19497.40]andthestandarddeviationis4002.243.Theskewnessofthepricesequenceisgreaterthan0andthekurtosisisgreaterthan3,andthedatapresentsthefeatureofpositiveskewnesspeak.AccordingtoitsJBstatisticof201.5989(Pvalue=0.00),itisnotzero,whichsignificantlyrejectstheassumptionthatthepricedeviationrateobeysthenormaldistributionwiththemeanvalueof0.Accordingtothesimplecalculation,therangevalueofBTCis19286.91,whichindicatesthatthepriceofBTCishighlydispersed,andthepriceisinitiallyconsideredtobeinabubble.ForETH,themaximumvalueis1396.420andtheminimumvalueis0.434829.Thereisadifferenceofmorethan3,000timesbetweenthetwo,whichshowsthelargepricerange.Theskewnessofthepricesequenceis1.728837,greaterthan0,andthekurtosisis6.129578.Itcanbeseenthattheshapeofthepricesequenceissimilartothatofbitcoin,bothofwhichshowapositiveskewnesspeak,andarealsonotnormallydistributed.Pricesarealsoextremelyfragmented,withinitialconfirmationofabubbleinEthereumprices.ForLTC,thedigitnumberis39.48andthepricerangeis[2.63,358.4].Thepricefluctuationrangeissmallerthanthatofbitcoin.Theskewnessofitspriceseriesis1.721271,andthekurtosisis6.420911,showingapositiveskewnesspeaklikeethers.AccordingtotheJBstatistics,LTCisnotnormallydistributed.Therangecanbecalculatedas355.71,andthepriceislessdispersedthanbitcoin.ForXRP,thepriceisrelativelysmall,withtheminimumvalueof0.00409andthemaximumvalueof3.38000.Theskewnessofthepricesequenceisgreaterthan0,andthekurtosisislarger,whichis21.09423,showingthefeatureofright-leaningpeak.Therangeissmall,andthepriceofXRPdispersiondegreeisverysmall.ForDASH,thepricerangeis[2.06,1550.85]andthestandarddeviationis225.2759,indicatingalargerangeofpricefluctuations.Theskewnessis2.530587andthekurtosisis10.58912,whicharealsointheformofpositiveskewnesspeak.Similarly,byusingthemethodofanalyzingtheaboveJBstatistics,itcanbeseenthatthepriceofDASHdoesnotfollowthenormaldistributionandtherangeislarge,indicatingthatthepriceisdispersed.Accordingtotheabovedescription,themarketvalueofdifferentvirtualcurrenciesdenominatedinusdollarshasasignificantlong-termdeviation,whichmakesusmoreconvincedofthepossibilityofspeculativebubblesintheabovefivevirtualcurrencies.5.2EmpiricaltestresultsAccordingtoPhillipsetal.(2011,2015),SADFandGSADFtesttheproportionofsamplesintheinitialwindow.Inordertodeterminethefirstregressionsample,thefollowingregressionmethodappliestheformular0=0.1+0.18Tandobtainsthecriticalvaluebyapplying10,000Table5.2SADFtestresultsforfivevirtualcurrenciesTestedcurrencyTestmethodWaldStatisticsBootstrapCriticalValueResult10%5%1%BTCSADF3.087451.975942.597522.95332Thereisaspeculativebubble.ETHSADF14.159889.172789.5708114.03321DSAHSADF14.448709.6856011.8361012.27075XRPSADF19.1651714.2285315.4705618.58839LTCSADF14.159889.172789.5708114.03321Table5.3GSADFtestresultsforfivevirtualcurrenciesTestedcurrencyTestmethodWaldStatisticsBootstrapCriticalValueResult10%5%1%BTCGSADF6.758334.216785.460855.57164Thereisaspeculativebubble.ETHGSADF14.497889.5868310.9176711.47854DSAHGSADF14.448709.6856011.8361012.27075XRPGSADF19.1651715.0373817.0270118.07643LTCGSADF14.1647510.6167013.2713514.08654Fromtheabovetwotables,itcanbeseenthattheT-testvaluesofthefivevirtualcurrenciesareallgreaterthanthecriticalvalueandareallgreaterthanthe99%criticalvalue,soitcanbepreliminarilyconcludedthatthepricesofthefivevirtualcurrenciesallhavespeculativebubbles.SoitcouldshowthatGSADFtestismoresensitivethanSADFtest.Inordertogiveamorevisualpictureofthefivepricebubblesinvirtualcurrencies,webartheperiodsofbubblesintheSADFandGSADFtestresults(seeFig1).Amongthem,thegreencurveisthepricetrendoffivevirtualcurrencies,thebluecurveistheSADFandGSADFvaluesofthepricesofeachvirtualcurrency,andtheredcurveisthecriticalvaluewhenthespeculativebubbleoccurs.Whenthebluecurveislargerthantheredcurve,thepricebubbleappears.WhentheBSADFstatisticexceedsitscriticalvalueforthefirsttime,thebubblebeginstoform.WhentheBSADFstatisticisbelowitsthresholdforthefirsttime,thebubbleisover.Byobservingtheshapeofthecurveinthefigure,itcanbeseenthatallfivecurrencieshavebubbles.Inparticular,BTChasthelargestcolumnararea,indicatingthatthecurrencyhasthelongesttermofspeculativebubbles.However,thenumberofXRPbarsisthehighest,whichindicatesthatbothBTCandXRPhaveseriouspricebubbles.Atthesametime,itcanbeseenthatin2017,fivekindsofvirtualcurrenciesallshowedbubbleslastingforalongtime,amongwhichanimportantreasonwasthelaunchofICO,orInitialtokenOffering.Inordertofurtherunderstandthespecifictimepointsoftheemergenceandburstingofspeculativebubblesoffivevirtualcurrencies,wehavelistedthebubbledurationoffivevirtualcurrencies(seeappendix2).BecausetheresultsoftheGSADFtestaresuperiortotheSADFtest,weonlyusethefinalresultsoftheGSADFtestandlistthebubbleperiodoftheGSADFtest.ItcanbeseenfromthetablethatthepriceofXRPhasthemostbubbles,withatotalof13bubbles,whileBTChasthelongestbubbleduration,withanaveragedurationof38.4days.TheGSADFtestisusedtodetectthebubbleburstingbehaviorassessmentdataandhastheflexibilityoflargerWindows(Phillipsetal.,2012,2013).AccordingtotheGSADFtestestimation,theconfidenceis95%ofthetimeinterval,wherethestartdateofthebubblerepresentsthefirstobservationthattheGSADFstatisticisgreaterthanthethresholdvalue,andtheenddateofthebubbleisdefinedasthefirstGSADFstatisticthatdropsbelowthethresholdvalueafterthestartdate.ThismethodperformsbetterthantheSADFtestafterverifyingthatthesampleGSADFextendsthesamplebymovingthesample.Detectingthesizeofbubbleburstingbehaviorespeciallyinmultiplebubbleevents,therearerareresultsinfalsealarmsbecauseGSADFtestsevaluateothersubsamplesoftheseries.Itcanbeprovedthattherearemultiplepricebubblesinthevirtualcurrencymarket.Conclusions6.1Bubblecauseanalysis6.1.1SpeculativedemandThemainreasonforpricebubblesisthatspeculativedemandstimulatesthecontinuousriseofprices.Digitalcurrencymarkettradingformis24hoursofuninterruptedtradingandthepricedoesnotlimitthelimit,inadditiontoavarietyofadvantages:simpleaccountopeningprocedures,lowfees,lowtransactionthresholdandtradingisnotsubjecttoanytime,spaceandgeographicalrestrictions.Itsgreatestadvantageconstantlyattractsinvestorstospeculate,sofinallyleadingtothe"herdeffect",whichwilleventuallyacceleratetheexpansionofthepricebubble.TakeBTC,whichfirstappearedinthedigitalcurrencymarket.InOctober2009,theexchangerateofbitcoinwasfirstannouncedas:1dollar=1309.03bitcoins.ByMay2010,10,000bitcoinscouldbeexchangedfor$50worthofpizzavouchers.ByJune19,2011,asMT.GOXwasattackedbyhackers,thepriceofbitcoinplungedfrom$17.51to$0.01.InApril2013,itspriceroseto$100duetotheboomingmarketandfavorableoveralleconomicenvironment.OnMarch28,2018,BTCclosedat$8,039.86perbitcoin.OnMarch7,2020,itclosedat$8,909.90pershare.Itcanbeseenthatthelargeriseandfallofbitcoinpricearebeneficialasafinancialspeculationobject,forwhichmanyinvestorsflocktoit.InDecember2013,BTC'smarketshareinChinawasclosedto70%oftheglobalmarket,andspeculationamongChineseinvestorswasanimportantdriverofthecurrency'srise.6.1.2LackofregulationIfthemeritsofdigitalcurrenciesthemselvesaretheunderlyingcauseofbubbles,thelackofregulationisanimportantexternalfactorbehindtheircontinuedexpansion.Theunderstandingandregulationofvirtualcurrencyvariesfromcountrytocountry.Thefollowingtableliststhemeasures,documentsandstatementsissuedbydifferentgovernmentsontheregulationofbitcoin.CountriessuchasRussia,Kyrgyzstan,Iceland,Bolivia,EcuadorandVietnamhaveimposedstrictbansonbitcoin.TheUnitedStates,Switzerland,Germany,Singaporeandothercountriesarerelativelylaxregulation.Since2013,whenthepriceofBTCbegantoboomandbubble,BTChasbecomeknowntomoreandmorepeople.Itcanbeseenfromtable6.1thatin2013,mostgovernmentsheldasupportiveattitudetowardsBTC.Germany,inparticular,wasthefirsttorecognizethetaxandlegalstatusofBTC.OnMay2013,theusgovernmentcrackeddownonillegaldrugtransactionsbyusingBTConthesilkroadwebsite.ThiscausedthepriceofBTCtofallforashorttime,butthenitspricerecoveredafterashorttime,whichisagoodindicationofspeculators'preferencefortheemergingvirtualcurrency,andalargenumberofspeculatorsboughtalargeamountofBTCduringthepricedeclineofBTC.Afterexperiencingaboomandbustin2013,digitalcurrenciesexperiencedanotherboomandbustinlate2017.Inadditiontothemajorreasonsmentionedabove,thereisanotherimportantfactor:ICO.Inthefirsthalfof2017,ICOraisedahugeamountofmoney,raisingasmanyas100,000people,andthepopularityofspeculatorsforBTCalsoincreased,resultinginthepricegraduallyrisingfromthebeginningof2017.However,thepriceofBTCbegantofallinJuneduetothemixednatureofICOprojectsonthemarket,whichmadeitdifficultforinvestorstodistinguishthetruefromthefalse,andtherewerevariousillegalfund-raisingactivitiesinICOprojects.ThischaosledtotheissuanceofanoticeonpreventingthefinancingriskoftokenissuanceinthepreviouslyunregulatedChinesemarket.ThisnoticeindicatedthatChinawouldstrictlybanICOprojects,closeexchangesandwithdrawBTCfromtheChinesemarket.BTCisbannedintheChinesemarket,JapanandSouthKorea,whileothercountriesstillholdafavorableattitudetowardsBTC,sothepriceofBTCisnotlargelyaffectedbythepoliciesoftheChinesegovernment.However,thepriceofBTCreachesthemaximuminthemiddleofDecember2017,whenthepricebubblewillburst.ThelaunchofBitcoinCashinAugust2017,whichdivertedBTC'scomputingpower,ledtoagradualsell-offbyinvestorsthatkeptbitcoinpricesonadownwardtrendthroughout2018.Table6.1TheregulationofvirtualcurrencyinvariouscountriesDateCountryIncident2013.05AmericaFinancialcrimeenforcementsystemissuesregulationsonvirtualcurrency.2013.08Thecourtruledthatbitcoinisacurrencyandshouldberegulatedbyfinancialregulations.2013.10Crackdownonillegaltradewebsite"silkroad".2013.11Ahearingisaboutbitcoin.2015.06NewYorkstateissuedBTClisencetocompaniesinthebitcoinindustry,thefirststatetolicensebitcoin.2013.11ChinaThecentralbankdoesnotrecognizebitcoin'slegalstatus.2013.12Thecentralbankissuedanoticeonpreventingrisksofbitcoin,makingitclearthatbitcoincannotbecirculatedinthemarketasacurrencyandisnotarealcurrency.2017.02Thecentralbankinterviewedthreebitcoinexchanges.2017.09Thepeople'sbankofChinaissuedthenoticeonpreventingthefinancingrisksoftokenissuance.2014.02RussiaOfficialshavedeclaredbitcointransactionsillegalandbannedfrombeingusedinRussia.2014SwitzerlandThefederalcommissionsaysitseesnoneedtoregulatecryptocurrencies.2016Thestate-ownedfederalrailroadcompanysellsbitcoinsthroughticketmachines,andseveralstateshaveacceptedbitcoinsaspayment.2013.08GermanyThecountryrecognizesbitcoin'slegalandtaxstatus.2013.12Thefederalbureauoffinancialsupervisionstatedthatbitcoinisnotacreditcurrency,butcanbeusedasameansofpaymentforprivatetransactionsandwilllikelybesubjecttoVAT.2014.03JapanBitcoinisnotconsideredacurrencyandistreatedasapreciousmetalwhosepricefluctuateswiththemarket.Banksorsecuritiescompaniesarenotallowedtoactastransactionintermediariesoropenspecialaccounts.2016.10Therevisedpaymentserviceslaw,whichcameintoeffectinApril2017,definestheconceptofvirtualcurrencyasa‘newpaymentmethod’ratherthanacreditcurrency.Itcanbeseenthatthelaxsupervisionofdigitalcurrencyinmanycountriesisanimportantreasonforthecontinuousexpansionofpricebubble.6.1.3MarketmanipulationFormorethanadecadeaftertheemergenceofdigitalcurrency,digitalcurrencyhasbeengrowingtenaciously,andpricebubbleshavealwaysexisted.Animportantreasonisthatitspriceiscontrolledbythemarket.TakingBTCasanexample,thetotalnumberofBTCislimitedto21million.ByFebruary2020,thenumberofBTCincirculationisabout17.9million,whichhasnotyetbeenminedout.Intermsofglobalmarketshare,asofDecember2016,theBTCtradingvolumeinChinaaccountedfor99.9%oftheglobaltradingvolume,whichcanbesaidtohavebeencompletelydominatedbytheChinesemarket.Themonopolyofthemarketleadstothepriceofbitcoinmarketiseasytobemanipulatedbydealers,sothereasonforthebubbleshouldalsoincludemarketmanipulation.6.1.4ChangesinthefinancialenvironmentFinancialenvironmentreferstothedevelopmentofglobalfinanceandmacroeconomicenvironment,anditsindicatorssuchasforeignexchangerate,stockindex,goldprice,oilpriceandothervariableswillalsoaffectthepriceofvirtualcurrency.Forexample,whengoldprice,oilprice,stockindexandsoonrise,itindicatesthattheoveralltrendofglobalmacroeconomyisupwardandthefinancialdevelopmentisgood,stimulatingthetransactionofvirtualcurrency.Soitmakesdemandincreasesandthepricerises.Butamacroeconomicrecessiondoesnotnecessarilyleadtoapositivetrendinvirtualcurrencyprices.Supposethatwhenthestockindexdropsandthestockpricedrops,someinvestorswillselltheirstocksandinvestinvirtualcurrenciestostimulatethegrowthofvirtualcurrencyprices.Thusitcanbeseenthatsomemajorinternationalanddomesticeventsmayhaveasignificantimpactontheglobalinvestmentenvironment.6.2Suggestionsonthedevelopmentofvirtualcurrencymarket6.2.1BuildaprofessionalvirtualcurrencytradingplatformThisplatformcanbeusedforreferencebystockexchanges.Forexample,therangeofriseandfallofpricescanberegulatedtoavoidawiderangeofriseandfallofprices.Openallthetradingreportstoachievetransparency,sothatinvestorscantimelyunderstandtheinformationdynamicsofthemarket,conducivetothedevelopmentofthemarket.6.2.2FormulatecorrespondingsupervisionmechanismThemarketneedstobeorderly.Forexample,itisnecessarytoaudittheinvestorsandsetupthethresholdforqualifiedinvestors.Meanwhile,itisnecessarytoevaluatetherisktoleranceandassetstatusoftheinvestors.Formulatecorrespondinglawsandregulationstoprohibitthesellingofinvestors'personalinformationwithouttheirpermission,andpreventvariousillegalACTSsuchasmoneylaundering.Theissuanceandcirculationofdigitalcurrencyshouldberegulatedandthecorrespondingregulatorybodiesshouldbedefined,andtheprocessshouldbecarriedoutunderthesupervisionofthenationalgovernment.Createarelativelysafeinvestmentenvironmentforinvestorsasmuchaspossible,strengthenthesupervisionofthefinancialmarket,andavoidthephenomenonofartificiallymanipulatingthecurrencyprice.6.2.3AcceleratetheimprovementofthevirtualcurrencysystemNow,somelargeenterprisesinChina,suchasAlibabaandTencent,havestartedtoprovidemoreconvenientservicesthroughcryptocurrency,andatthesametime,theyhavemadeupfortheshortcomingsintheInternetfield.Theyarelovedbymostenterprises.Itisbelievedthatinthenearfuture,virtualcurrencywillbewidelyusedandgraduallyacceptedbythepublic.Therefore,therecognitionandimprovementprocessofthevirtualcurrencysystemcannotbeignored.Therefore,itisnecessarytoconsolidateandstrengthenitsbasicresearchandacceleratethedevelopmentofvariousemergingtechnologiessuchas5G,blockchainandbigdata.Then,itisnecessarytobuildatechnologyresearchanddevelopmentsystemaboutvirtualcurrency,strivingforinnovation,strivingfortechnologyintegrationwithotherrelatedcross-disciplines,andpromotescientificdevelopment.Finally,asfortheprivatizationofvirtualcurrency,thestateshouldmakeeffortstopromotelegaldigitalcurrencyandgiveplaytothestate'smacro-controlabilityoftheeconomy.Inaddition,thepreventionandcontrolofriskscannotbeignored.Therefore,correspondingtransactionriskwarningmechanismshouldbesetuponthevirtualcurrencysystem.Itisspecializedtoobservethetotalamountoftradinginformationinthetradingplatform.Ifanyabnormalsituationoftradingoccurs,itcanbehandledintimetopreventtheoccurrenceofanyunexpectedthingsduetoabnormaloperationoftheentiretradingsystem.6.2.4GuideinvestorstoinvestrationallyThegovernmentneedstomakeuseoftheadvantagesofpoliciesandtheadministrativeinterventionofeconomicauthorities.Itshouldunderstandandmanagethepublicinvestmentexpectation,reasonablyguidethepublictomakelegitimateandrationalinvestment,andavoidirrationalinvestment,soastostabilizethefinancialmarket.Reasonablyguideinvestorstoinvest.Forexample,itisnecessarytopopularizethebasicknowledgeofvirtualcurrencyandthepossiblerisksofinvestinginvirtualcurrencytoinvestors,strengthentheeducationofinvestors,andavoidirrationalthinkingandblindlyfollowingthetrend,leadingtothelossoftheirassets.Investorsshouldalsoconsciouslylearnandunderstandallkindsofbasicknowledgeofvirtualcurrency,andtrytoavoidirrationalinvestmentbehavior,soastoavoidtheoccurrenceofpricebubblesinthevirtualcurrencymarketandstabilizethefinancialmarket.6.3DeficienciesandfutureresearchdirectionsAsfortheshortcomingsofthispaper,firstly,theSADFandGSADFdetectionmethodsadoptedinthispaperarebasedonthemodelframeworkofrationalbubbles,anddonotconsiderthepossiblesituationofirrationalbubbles,sotheresultsmaybebiased.Then,theconclusionsofthispaperarebasedonhistoricaldataandcanonlybetestedafterthefact,andcannotbepredictedinadvance.Therefore,itisimpossibletopreventvariousrisksinadvance.Finally,allthefivecurrenciesinthispaperaredenominatedinusdollars,andtheresultsmaynotberigorousbecausetheyarenotcomparedwithotherfactorssuchasexchangeratesbetweendifferentcountries.Therefore,inthelaterstudy,duetotheirrationalbubbleisexpectedinallkindsofproblemsorinreallifeplayanimportantrolethatarenotallowedtoignore,sowewilltrytostudyrelatedknowledge,andtoexploretheeconometricmodelofirrationalbubbles,attachimportancetotheriskwarningandpreventionatthesametime,toadvancetheprejudgment.

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