写目前的热门话题：

　　ThesubprimemortgagecrisisisanongoingproblemmanifestingitselfthroughliquidityissuesinthebankingsystemowingtoforeclosureswhichacceleratedintheUnitedStatesinlate2006andtriggeredaglobalfinancialcrisisduring2007and2008.ThecrisisbeganwiththeburstingoftheUShousingbubbleandhighdefaultrateson"subprime"andotheradjustableratemortgages(ARM)madetohigher-riskborrowerswithlowerincomeorlessercredithistorythan"prime"borrowers.Loanincentivesandalong-termtrendofrisinghousingpricesencouragedborrowerstoassumemortgages,believingtheywouldbeabletorefinanceatmorefavorabletermslater.However,oncehousingpricesstartedtodropmoderatelyin2006-2007inmanypartsoftheU.S.,refinancingbecamemoredifficult.DefaultsandforeclosureactivityincreaseddramaticallyasARMinterestratesresethigher.During2007,nearly1.3millionU.S.housingpropertiesweresubjecttoforeclosureactivity,up79%versus2006.AsofDecember22,2007,TheEconomistestimatedsubprimedefaultswouldreachalevelbetweenU.S.$200-300billion.

　　Themortgagelendersthatretainedcreditrisk(theriskofpaymentdefault)werethefirsttobeaffected,asborrowersbecameunableorunwillingtomakepayments.MajorbanksandotherfinancialinstitutionsaroundtheworldhavereportedlossesofapproximatelyU.S.$170billionasofFebruary2008,ascitedbelow.Owingtoaformoffinancialengineeringcalledsecuritization,manymortgagelendershadpassedtherightstothemortgagepaymentsandrelatedcredit/defaultrisktothird-partyinvestorsviamortgage-backedsecurities(MBS)andcollateralizeddebtobligations(CDO).Corporate,individualandinstitutionalinvestorsholdingMBSorCDOfacedsignificantlosses,asthevalueoftheunderlyingmortgageassetsdeclined.Stockmarketsinmanycountriesdeclinedsignificantly.

　　Thewidespreaddispersionofcreditriskandtheuncleareffectonfinancialinstitutionscausedlenderstoreducelendingactivityortomakeloansathigherinterestrates.Similarly,theabilityofcorporationstoobtainfundsthroughtheissuanceofcommercialpaperwasaffected.Thisaspectofthecrisisisconsistentwithacreditcrunch.Theliquidityconcernsdrovecentralbanksaroundtheworldtotakeactiontoprovidefundstomemberbankstoencouragethelendingoffundstoworthyborrowersandtore-invigoratethecommercialpapermarkets.

　　Thesubprimecrisisalsoplacesdownwardpressureoneconomicgrowth,becausefewerormoreexpensiveloansdecreaseinvestmentbybusinessesandconsumerspending,whichdrivetheeconomy.Aseparatebutrelateddynamicisthedownturninthehousingmarket,whereasurplusinventoryofhomeshasresultedinasignificantdeclineinnewhomeconstructionandhousingpricesinmanyareas.Thisalsoplacesdownwardpressureongrowth.WithinterestratesonalargenumberofsubprimeandotherARMduetoadjustupwardduringthe2008period,U.S.legislatorsandtheU.S.TreasuryDepartmentaretakingaction.Asystematicprogramtolimitordeferinterestrateadjustmentswasimplementedtoreducetheeffect.Inaddition,lendersandborrowersfacingdefaultshavebeenencouragedtocooperatetoenableborrowerstostayintheirhomes.TheriskstothebroadereconomycreatedbythefinancialmarketcrisisandhousingmarketdownturnwereprimaryfactorsintheJanuary22,2008de