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Derivative-Option Greeks

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  1. 1. Using "The Greeks" To Understand OptionsJuly 01 2010| Filed Under » Bonds, Derivatives, Option Pricing, Options, ROCTrying to predict what will happen to the price of a single option or a position involving multipleoptions as the market changes can be a difficult undertaking. Because the option price does notalways appear to move in conjunction with the price of the underlying asset, it is important tounderstand what factors contribute to the movement in the price of an option, and what effectthey have.Options traders often refer to the delta, gamma, vega and theta of their option positions.Collectively, these terms are known as the "Greeks" and they provide a way to measure thesensitivity of an options price to quantifiable factors. These terms may seem confusing andintimidating to new option traders, but broken down, the Greeks refer to simple concepts that canhelp you better understand the risk and potential reward of an option position.Finding Values for the GreeksFirst, you should understand that the numbers given for each of the Greeks are strictlytheoretical. That means the values are projected based on mathematical models. Most of theinformation you need to trade options - like the bid, ask and last prices, volume and open interest- is factual data received from the various option exchanges and distributed by your data serviceand/or brokerage firm.But the Greeks cannot simply be looked up in your everyday option tables. They need to becalculated, and their accuracy is only as good as the model used to compute them. To get them,you will need access to a computerized solution that calculates them for you. All of the bestcommercial options-analysis packages will do this, and some of the better brokerage sitesspecializing in options (OptionVue & Optionstar) also provide this information. Naturally, youcould learn the math and calculate the Greeks by hand for each option. But given the largenumber of options available and time constraints, that would be unrealistic. Below is a matrixthat shows all the available options from December, January and April, 2005, for a stock that iscurrently trading at $60. It is formatted to show the market price, delta, gamma, theta, and vegafor each option. As we discuss what each of the Greeks mean, you can refer to this illustration tohelp you understand the concepts.
  2. 2. The top section shows the call options, with the put options in the lower section. Notice that thestrike prices are listed vertically on the left side, with the carrot (>) indicating that the $60 strikeprice is at-the-money. The out-of-the-money options are those above 60 for the calls and below60 for the puts, while the in-the-money options are below 60 for the calls and above 60 for theputs. As you move from left to right, the time remaining in the life of the option increasesthrough December, January, and April. The actual number of days left until expiration is shownin parentheses in the column header for each month.The delta, gamma, theta, and vega figures shown above are normalized for dollars.To normalizethe Greeks for dollars you simply multiply them by the contract multiplier of the option. Thecontract multiplier would be 100 (shares) for most stock options. How the various Greeks moveas conditions change depends on how far the strike price is from the actual price of the stock andhow much time is left until expiration.As the Underlying Stock Price Changes - Delta and GammaDelta measures the sensitivity of an options theoretical value to a change in the price of theunderlying asset. It is normally represented as a number between minus one and one, and itindicates how much the value of an option should change when the price of the underlying stockrises by one dollar. As an alternative convention, the delta can also be shown as a value between-100 and +100 to show the total dollar sensitivity on the value 1 option, which comprises of 100shares of the underlying. So the normalized deltas above show the actual dollar amount you willgain or lose. For example, if you owned the December 60 put with a delta of -45.2, you shouldlose $45.20 if the stock price goes up by one dollar.Call options have positive deltas and put options have negative deltas. At-the-money optionsgenerally have deltas around 50. Deep-in-the-money options might have a delta of 80 or higher,while out-of-the-money options have deltas as small as 20 or less. As the stock price moves,delta will change as the option becomes further in- or out-of-the-money. When a stock optiongets very deep-in-the-money (delta near 100), it will begin to trade like the stock, moving almostdollar for dollar with the stock price. Meanwhile, far-out-of-the-money options wont move
  3. 3. much in absolute dollar terms. Delta is also a very important number to consider whenconstructing combination positions.Since delta is such an important factor, option traders are also interested in how delta maychange as the stock price moves. Gamma measures the rate of change in the delta for each one-point increase in the underlying asset. It is a valuable tool in helping you forecast changes in thedelta of an option or an overall position. Gamma will be larger for the at-the-money options, andgets progressively lower for both the in- and out-of-the-money options. Unlike delta, gamma isalways positive for both calls and puts. (For further reading on position delta, see the article:Going Beyond Simple Delta, Understanding Position Delta.)Changes in Volatility and the Passage of Time - Theta and VegaTheta is a measure of the time decay of an option, the dollar amount that an option will lose eachday due to the passage of time. For at-the-money options, theta increases as an option approachesthe expiration date. For in- and out-of-the-money options, theta decreases as an optionapproaches expiration.Theta is one of the most important concepts for a beginning option trader to understand, becauseit explains the effect of time on the premium of the options that have been purchased or sold. Thefurther out in time you go, the smaller the time decay will be for an option. If you want to ownan option, it is advantageous to purchase longer-term contracts. If you want a strategy that profitsfrom time decay, then you will want to short the shorter-term options, so that the loss in valuedue to time happens quickly.The final Greek we will look at is vega. Many people confuse vega and volatility. Volatilitymeasures fluctuations in the underlying asset. Vega measures the sensitivity of the price of anoption to changes in volatility. A change in volatility will affect both calls and puts the sameway. An increase in volatility will increase the prices of all the options on an asset, and adecrease in volatility causes all the options to decrease in value.However, each individual option has its own vega and will react to volatility changes a bitdifferently. The impact of volatility changes is greater for at-the-money options than it is for thein- or out-of-the-money options. While vega affects calls and puts similarly, it does seem toaffect calls more than puts. Perhaps because of the anticipation of market growth over time, thiseffect is more pronounced for longer-term options like LEAPS.Using the Greeks to Understand Combination TradesIn addition to getting the Greeks on individual options, you can also get them for positions thatcombine multiple options. This can help you quantify the various risks of every trade youconsider, no matter how complex. Since option positions have a variety of risk exposures, andthese risks vary dramatically over time and with market movements, it is important to have aneasy way to understand them.Below is a risk graph that shows the probable profit/loss of a vertical debit spread that combines10 long January 60 calls with 10 short January 65 calls and 17.5 calls. The horizontal axis showsvarious prices of XYZ Corp stock, while the vertical axis shows the profit/loss of the position.The stock is currently trading at $60 (at the vertical wand).
  4. 4. The dotted line shows what the position looks like today; the dashed line shows the position in30 days; and the solid line shows what the position will look like on the January expiration day.Obviously, this is a bullish position (in fact, it is often referred to as a bull call spread) and wouldbe placed only if you expect the stock to go up in price.The Greeks let you see how sensitive the position is to changes in the stock price, volatility andtime. The middle (dashed) 30-day line, halfway between today and the January expiration date,has been chosen, and the table underneath the graph shows what the predicted profit/loss, delta,gamma, theta, and vega for the position will be then.ConclusionThe Greeks help to provide important measurements of an option positions risks and potentialrewards. Once you have a clear understanding of the basics, you can begin to apply this to yourcurrent strategies. It is not enough to just know the total capital at risk in an options position. Tounderstand the probability of a trade making money, it is essential to be able to determine avariety of risk-exposure measurements. (For further reading on options price influences, see thearticle: Getting to Know the Greeks.)Since conditions are constantly changing, the Greeks provide traders with a means ofdetermining how sensitive a specific trade is to price fluctuations, volatility fluctuations, and the
  5. 5. passage of time. Combining an understanding of the Greeks with the powerful insights the riskgraphs provide can help you take your options trading to another level.Read more: