以2003年造市者的逐筆報價資料進行實證，主要發現如下： 1. 2003年台指選擇權造市者的平均價差點數高達20.42點，平均價差百分比則為38.81%。導致造市者高報價價差的主因為TAIFEX規定的最大價差限制過於寬鬆，造市者總是以最大價差進行報價，報價價位並有聚集於整點位數的現象，升降單位的限制則不構成報價價差無法調降的理由。 2. 造市者的時間加權報價價差並無顯著日內型態，但與交易活絡度之間有顯著負向關係，並與風險、資訊與限價單價差之間有顯著正向關係。這個結果隱含造市者對交易愈熱絡的選擇權合約會要求較小的價差，並對風險較大的契約或在風險較高的時段提高報價價差，當市場有異常大單產生時，造市者會提高價差以避免與資訊交易者對作，限價單交易者的競爭則會使造市者縮小價差。 The bid-ask spreads quoted by market makers in the Taiwan Index Optoion market are investigated in this study. Using tick-by-tick quote data for the entire year of 2003, an average 20.42 index points of bid-ask spread is obtained. The binding tick size and the price clustering are first used to explain the wide quoted spread. Empirical results show that both tick size and price clustering can not entirely explain the large spread. The huge spread results from a loose spread limit set by Taiwan Futures Exchange and usually adopted by market makers. Four determinants of spreads provided by Schwartz (1988) are also employed to explain the market maker''s intraday spreads. Results indicate that market makers require less spreads for liquidity provision when options are more active and when limit order spreads are narrower. However, market makers'' spreads are widened when options are riskier and when large trades occur.
