In a relative lower position of the market index or the last period of a " bear " , larger - size ipos can get better return than market portfolio , while in a relative higher position of the market index or the initial period of a " bear " , smaller - size ipos can get better return than market portfolio . small - firm effect is obviously existed for new issues . 4 ) as for the ipos return of every month in a year , the returns of march , april , june are generally get the highest three ranks among all 12 months 實(shí)證表明:新股二級市場中長期收益表現(xiàn)顯著好于市場組合,上市后第二和第四年超常收益增加顯著;新股二級市場的中長期收益基本呈現(xiàn)右偏的尖頂峰分布形態(tài);新股上市后存在短期內(nèi)反應(yīng)過度的特點(diǎn),新股中長期的高超常收益主要由中小型市值的股票貢獻(xiàn),故我國股市基本屬于資金推動(dòng)型的市場,并存在中小盤股票的嚴(yán)重高估和投機(jī)性炒作問題。