Grossman, SanfordJ.,and JosephE. Stiglitz.1980. "On the Impossibility of
Informationally Efficient Markets." AmericanEconomicReview,70(3): 393-408.
Aspointedoutbya numberofscholars, ina worldofdispersedinformation, the
equilibriumpricewillitselfingeneralbe a sourceofinformation toparticipants,
sinceitincorporates whateverinformation otherparticipants have.Grossmanand
Stiglitzexaminetheimplicationforthecasewhereinformation canbeacquiredat
a cost.Ifthereisanequilibrium, somewillchoosetogetinformed andothersnot;
thetwocoursesofactionmustbe indifferent. (Veryspecialassumptions aremade
abouttheriskaversioncharacteristics ofthepopulationandaboutitsheterogeneity.)
Inparticular, ifsomeindividuals canacquireperfect information atafinite cost,then
noequilibriumexists,since,ifinformation isacquiredbysome,itwillbereflected
inthepriceandso canbe acquiredcostlesslybyothers, whileifnooneacquires
information, itwillpayanyindividual toacquireit.