證交所自開業以來,為因應市場需求,歷經多次升降單位修改動作;本文欲探討發生於2005年3月1日調整股價升降單位事件是否會對台灣股票市場之品質造成影響。以此日為調整股價升降單位的事件發生日,研究樣本將此期間內納入台灣五十之股票做為基準,除了探討升降單位改變前後對於買賣價差、市場深度、報酬波動性與成交量之影響外,並利用簡單線性迴歸與非線性迴歸模型探討股票報酬波動性、週轉率、價格倒數、升降級距和元月效應對於買賣價差及市場深度是否有影響。最後,再以其它學者所提出不同的計算指標,進行強韌性檢定,視其結果是否具一致性。 本文發現,台灣證券交易所於2005年3月1日升降單位的縮減措施,確實會造成買賣價差與波動性的降低,進而提升市場品質。另外再使用迴歸模型探討,則可發現波動性對買賣價差有正的影響,且升降單位的下降使得買賣價差顯著下降,提升市場品質;而波動性與市場深度則呈反向相關,升降單位的下降導致市場深度下降,價格波動大,市場品質低落。
The tick-size of stock price had been adjusted to a more minimum spread in the Taiwan stock market. Nearly, the Taiwan Stock Exchange changed the tick-size on March 1, 2005. This paper examines how market quality change after reduction of the tick-size. It exhibits a significant decrease in the bid-ask spread, market volatility, while improving market quality. Moreover, the market volatility and the spread have the same influence on the regression model. As such, reducing the tick-size would decrease the spread and increase market quality. Finally, decreasing the tick-tsize reduced the market depth and decreased market quality caused by the higher volatility.