期權賣方賺錢法寶—希臘字母Theta
期權賣方（Call Seller/Writer）是指賣出期權合約的一方。可以賣出的標的物有：認購期權（看漲期權）和認沽期權（看跌期權）。開倉賣出期權通常稱爲建立期權空頭（Options Short）頭寸。針對期權賣方來說，主要的盈利方式是賺取“時間價值”，針對時間價值，期權中用Theta來計算。
無論看漲期權還是看跌期權，隨着時間的流逝價值都會逐漸下降。Theta主要是測量時間變化對期權價值的影響。表示時間每經過一天，期權價值會損失多少。一般在期權軟件上都是顯示期權價值每日下降的點數。如果告訴你一個期權的Theta是-0.06，就表示在其他條件不變的情況下，期權價格會每天下降0.06，如果期權今天的價值是9.06，那麼明天期權的價值就是9。隨着到期日的臨近，時間價值損耗會加速。Theta以非線性方式影響期權價值。
Theta的正負該如何理解？
跟之前的希臘字母Delta，Gamma一樣，先看Theta的符號。顯然從定義上看，Theta表示的是期權價值隨時間的損失，所以對期權的買方來說，Theta值一般寫成負值，而對於期權的賣方來說，天然賺取時間價值的錢，所以寫成正的。
當你選擇作爲期權買方，就選擇了對抗自然規律—與時間損耗爲敵，必須克服其對期權價格的下拉作用。這張合約從誕生之日起，直至到期，每一天期權的外在價值都在減少。這就好比一輛裝滿河沙的卡車，在開往目的地的途中，不斷將沙子漏在地上。如果我們把這些「沙子」全部拾起,算一個總數，會發現剛好等於期權合約的外在價值。而賣方恰恰賺的正是這些每天不斷漏在地上的沙子。
作爲期權買方,擁有了正Gamma,且損失一開始就是確定的(風險兜底) ,但它的Theta卻爲負數。作爲期權賣方,雖然是負Gamma,損失可能會很大(風險開口），但卻拿到了正Theta，利用時間損耗賺錢。
Theta與到期日和執行價的關係
執行價方面，平值期權附近的Theta讀數最大，而分別往兩邊,進入ITM或OTM狀態，Theta都在逐漸縮小。
隨着到期日臨近，如果期權合約處在平值狀態附近，Theta曲線會被逐漸擡高，Theta讀數增大。如果期權合約處在深度OTM或深度ITM狀態，Theta曲線會被逐漸壓低，趨近於X軸，Theta讀數縮小。
這意味着越靠近到期日，靠近平值狀態的期權的外在價值會加速衰減。而深度的實值或虛值狀態，外在價值衰減的速度反而慢了下來。
Theta與波動率
Theta還和一個重要因素有直接關係，這個因素便是波動率。期權賣方總是想要在波動率高的時候賣期權，也是因爲波動率和期權的Theta絕對值成線性正比。這意味着，波動率越高，期權的Theta絕對值便越大，越有利於賣方賺取時間值。
Follow us
Find us on
Facebook,
Twitter ,
Instagram, and
YouTube or frequent updates on all things investing.Have a financial topic you would like to discuss? Head over to the
uSMART Community to share your thoughts and insights about the market! Click the picture below to download and explore uSMART app！
Disclaimers
uSmart Securities Limited (“uSmart”) is based on its internal research and public third party information in preparation of this article. Although uSmart uses its best endeavours to ensure the content of this article is accurate, uSmart does not guarantee the accuracy, timeliness or completeness of the information of this article and is not responsible for any views/opinions/comments in this article. Opinions, forecasts and estimations reflect uSmart’s assessment as of the date of this article and are subject to change. uSmart has no obligation to notify you or anyone of any such changes. You must make independent analysis and judgment on any matters involved in this article. uSmart and any directors, officers, employees or agents of uSmart will not be liable for any loss or damage suffered by any person in reliance on any representation or omission in the content of this article. The content of the article is for reference only and does not constitute any offer, solicitation, recommendation, opinion or guarantee of any securities, virtual assets, financial products or instruments. Regulatory authorities may restrict the trading of virtual asset-related ETFs to only investors who meet specified requirements. Any calculations or images in the article are for illustrative purposes only.
Investment involves risks and the value and income from securities may rise or fall. Past performance is not indicative of future performance. Please carefully consider your personal risk tolerance, and consult independent professional advice if necessary.
