12“”“”3T+0512BBBBB10003412341SpeculationIB100251250(”(2)(3)”2“”3¾¾¾¾¾“”12(Demsetz1968)(Demsetz1968)SEC(1971)(BenstonandHagerman1974)(Garman1976)(Stoll1978)(CohenMaierSchwartzandWhitcombCMSW1981)—(HoandStoll198l1983)3(Bagehot1-971)1“”“”2“”12——continuousdealermarket123