股票期权的英文文献

MANAGEMENTSCIENCEVol.55,No.4,April2009,pp.513–525issn0025-1909eissn1526-55010955040513informs®doi10.1287/mnsc.1080.0958©2009INFORMSWhatFractionofStockOptionGrantstoTopExecutivesHaveBeenBackdatedorManipulated?RandallA.HeronKelleySchoolofBusiness,IndianaUniversity,Indianapolis,Indiana46202,[e-mail]fBusiness,UniversityofIowa,IowaCity,Iowa52242,[e-mail]13.6%ofalloptiongrantstotopexecutivesduringtheperiod1996–2005werebackdatedorotherwisemanipulated.Ourstudyprimarilyfocusesongrantsthatwereunscheduledandat-the-money,ofwhichweestimatethat18.9%weremanipulated.Thefractionis23.0%beforethenewtwo-dayfilingrequirementtookeffectonAugust29,2002,and10.0%afterward.Fortheminorityofgrantsthatarenotfiledwithintherequiredtwo-daywindow,thefractionofmanipulatedgrantsremainsashighas19.9%.Wefurtherfindahigherfrequencyofmanipulationamongtechfirms,smallfirms,andfirmswithhighstockpricevolatility.Inaddition,firmsthatusesmaller(non-big-five)auditingfirmsaremorelikelytofiletheirgrantslate.Finally,atthefirmlevel,weestimatethat29.2%offirmsmanipulatedgrantstotopexecutivesatsomepointbetween1996and2005.Keywords:executivecompensation;stockoptiongrants;backdatingHistory:ReceivedAugust7,2007;acceptedOctober19,2008,byDavidA.Hsieh,finance.PublishedonlineinArticlesinAdvanceJanuary28,2009.1.IntroductionYermack(1997)findsthatfirms’stockreturnsareab-normallyhighimmediatelyafterexecutivestockop-tiongrants,andAboodyandKasznik(2000),ChauvinandShenoy(2001),Collinsetal.(2005a,b),Lie(2005),HeronandLie(2007),andNarayananandSeyhun(2008)alsofindthatthereturnsareabnormallylowbeforethegrants.Thelatterfourstudiesfindevidencethatbackdating,i.e.,pickingapastdateonwhichthestockpricewasparticularlylowtobethegrantdate,contributestothisstockpricepattern.HeronandLie(2007,p.294)concludethat“backdatingisthemajorsourceoftheabnormalstockreturnpat-ternsaroundexecutivestockoptiongrants”andthatitcanexplain“most,ifnotall,ofthepattern”instockreturnsaroundgrants.However,theextantresearchdoesnotspecificallyattempttodiscernthefractionofgrantsthatareback-datedorotherwisemanipulated.Whatwedoknowisthatthemedia,principallystartingwithaWallStreetJournalarticle(ForelleandBandler2006),haveiden-tifieddozensofsuspectfirms,firmsunderformalinvestigation,andfirmsthathaveadmittedirregu-laritiesintheaccountingoftheiroptiongrantdates.Forexample,attheendofOctober2006,theWallStreetJournalOnline(2006)reportedthatatleast120firmshavecomeunderscrutinyforpastoptiongrants.AsofMarchof2007,aGlass-LewisreportindicatedthatthenumberoffirmsthateitherhadannouncedinternalreviewsorhadbeenthesubjectoftheU.S.SecuritiesandExchangeCommission(SEC)and/orU.S.DepartmentofJusticeinvestigationsintotheiroption-grantingpracticeshadincreasedto257.Fur-thermore,DerekMeisner,aformerbranchchiefintheenforcementdivisionoftheSEC,statedthatheis“notawareofacorporatepracticethathascomeundersuchscrutinybytheSEC”(AnandandArnold2006).Clearly,themagnitudeoftheoptiongrantmanipu-lationproblemisofgreatinteresttoboththeinvest-mentcommunityandregulators,anditisthesubjectofspeculationinthemedia.Thisstudyprovidessomeestimatesonthefractionofgrantstotopexecutivesthathavebeenbackdatedormanipulatedinsomefashion.Anotherimportantcontributionisthatweexaminetheeffectsoffirmcharacteristicsandtheidentityoftheauditoronthedecisiontomanipulategrantdates.Ourestimationmethodologyrestsontheassump-tionthat,intheabsenceofbackdatingorothertypesofgrantdatemanipulation,thedistributionsofstockreturnsduringthemonthbeforeandaftergrantdatesshouldberoughlythesame,implyingthatthedis-tributionofreturndifferencesshouldbecenteredonzero.Thisallowsustoinferthefractionofgrantsthatmusthavebeenmanipulatedbycontrastingthedis-tributionoftheobservedreturndifferenceswithwhat513HeronandLie:WhatFractionofStockOptionGrantstoTopExecutivesHaveBeenBackdatedorManipulated?514ManagementScience55(4),pp.513–525,©2009INFORMSthedistributionshouldbeintheabsenceofgranttiming.Onemightarguethatfirmsmightmerelygrantoptionsafterstockpricedeclines,e.g.,aneg-ativemacroeconomicshock.However,theempiricalevidenceinHeronandLie(2007)doesnotsupportthisconjecture,becausethenegativeabnormalreturnsbeforeoptiongrantsareabsentforthesubsetoftheirsamplethatreportedoptiongrantsimmediately.Weexplainourestimationprocedurealongwithpotentialbiasinfurtherdetaillater.Oursampleconsistsof39,888stockoptiongrantstotopexecutivesthatweredatedbetweenJanuary1,1996,andDecember1,2005.Weestimatethat13.6%ofthesegrantsweremanipulated.However,therearesignificantdifferencesacrosstimeperiods,companytypes,grantcharacteristics,andevenauditors.Accountingconventionandtaxrulesprovideincen-tivesforcompaniestopricethemajorityoftheirop-tiongrantstobeat-the-money(i.e.,tosettheexercisepricetobeequaltothemarketprice)onthepurportedgrantdate(seeHeronandLie2007forfurtherdis-cussion).Ifcompanieschoosenottogranttheoptionsat-the-money,theincentivetomanipulatethegrantdateismuted.Moreover,ifgrantsarescheduledtooccuronacertaindateeveryyear,theopportunityformanipulatingthegrantdateisabsent.Thus,theremainderofouranalysisfocusesonunsc