But it will be like death by paper cuts with all the commission and tiny slippage paid. One of the reasons why people invented variance swaps was that they did not want to manage delta yet did want the exposure to realized volatility. And with gamma comes delta, so you have to dynamically manage it. You can pick a highly liquid option and let your system to constantly rebalance the short straddle by closing the old one and open new atm ones as the underlying moves x point away. OTM options but I was wondering what other strategies exist to meet the above two criteria without using Calendar spreads. Iron condor also has a big delta risk on most combinations. Can you tell us why you want to avoid time spreads? Gamma neutral only using options.
Theta is gamma in reverse. Volatility Trading, it goes through this stuff in detail. Is there any way to meet this two criteria without using Calendar spreads? Its still unclear on how this process works. Theta decay and I have a question around Theta decay. Maybe the pros can comment if any fund actually do this, i doubt it. The risk we are willing to assume is volatility. Numerical rounding and precision is an issue in the calculations of the Greeks here, but we can see that there is almost no difference between any of the Greeks along a line.
We discovered in the last article that theta for an option is negative: as time passes the value of an option decreases. Now we look at the PnL for a put and a share. This reduction in expectation implies a low price for the option with days left before expiration. USD, the price we paid for the call. This plot was surprising, and confirmed something suggested at by the earlier plots: the premium decay for ITM and OTM options are very similar. The gamma of the option is 10. Note the calculations should be exact except for small rounding discrepancies. What happens if the stock price moved 1 USD over the period of a trading day instead? In the third post in this series on volatility and options trading we investigate the effects and trading implications of input behaviours on the option price.
This means if the stock price goes up, the delta of the call will be around 40. We will draw all three plots together. In the fourth and final article of this series I will discuss vol: its effect on prices, how we think about it, and how it behaves as the underlying moves. This makes sense, option premium is an expectation of future possible value and as time passes there is less opportunity for the stock to move and realise that value. Note that the gamma has also increased, so further increases in share price will accelerate the gains in option price further. Price parity forces this. In a live environment, the stock price is moving around, meaning that when the stock is close to the strike, the change in deltas is large, and hedging deltas to reduce risk will be expensive and counterproductive.
So, if nothing happens but the passing of time, the Gamma of the option will increase, then rapidly move to zero once 10 days or less are left in the option. Similar to the ATM case, the option value decay approximates a constant rate, but loses almost all value earlier than the ATM option. If the price had gone through the strike and kept going, it would start to lose pace, as the gamma would start to decrease, but the options would also have intrinsic value. Why is this relevant? What would happen if the price had gone down by 1 USD instead of up? We compare this to a having two puts and being long a share. Options provide significant leverage, large gammas cause small changes in the underlying to have a huge effect in the option price. The behaviour of implied vol is a major component of options trading, and we discuss it in the final article. After one day, the stock moved up to 100 USD, and we need to recalculate the price of the call for the new stock price and time to maturity. An immediate consequence of the time decay of premium is that owning options is expensive.
This is exactly true for European options but still holds approximately for American options. Historically, option prices were quoted in expiration and strike order, with the strike prices in a column down the centre, the call prices on the left of this column and the put prices on the right. For deep in or out of the money options, the gamma of the option is zero, and the delta of the option is close to either zero or 100. The 105 Put will decay in a very similar way to the 95 Call. It is worth spending time unpicking all this as there are a few things to consider. This means the option gains value from a rising share price, so we expect the stock price to go up. Gamma, the second derivative of the option price to changes in the underlying. Furthermore, what does it mean if the gamma is increasing?
What is the PnL in this case, and how does it compare to being long the 100 put and long the stock instead? Is there an intuitive reason for this? For example, suppose we are long a 30 delta call. The code used to produce all of the above graphs and numbers is available in BitBucket repo if you would like to use it yourself. Note that the ITM and OTM options are 5 USD from the underlying of 100. Again, our guess is close enough.
The stock has more time to get to 100. USD of option premium. For now, we have enough complexity with vol constant! It is becoming apparent how complicated options behaviour can be. It helps develop our intuition. That said, some behaviours discussed do not hold for all options, especially for options with longer expirations, so beware! We rely on intuition about the outcomes for an explanation. Both affect this outcome distribution. Recall that a straddle spread is a call and a put on the same line.
In the second, we had 19 days. What does the option price do? ITM call is similar to the premium in the put from the same line. For the long put and stock, it is negative 101. Quite a narrow disparity, but we have forgotten to include interest on the cash balances. Long option positions are always long gamma. If we remove the intrinsic value and focus solely on the premium in the ITM option, how does this behave? USD at lunchtime on Friday. Our intuition also suggests that the new value for gamma will be lower. As we are long deltas, a fall in share price reduces the price of the option, and the positive gamma means that the delta also decreases.
If the market moves out of line on this, trading arbitrage will force it back. This seems like quite a bold claim so we should check it. Get it wrong, and you can lose a lot of money very quickly. It shows that as expiration approaches, deltas change a lot. My original plan for this series was to have three articles, and this final post would include discussions on the effect of vol and how to view option contracts as insurance, but that was wishful thinking! As each day passes, more and more value in your portfolio erodes away, and this is difficult from a psychological point of view. Premium in ATM options is more durable but then decays rapidly as expiration is imminent. But how does this decay happen? We use European options, because QuantLib gives use the Greeks automatically. The intrinsic value of the option is zero throughout, so the price decreases to zero at expiration.
This effect becomes much more pronounced in the final few days before expiration. Hence a particular combination of strike and expiration was a line in the price column. The gamma increase is puzzling. We also need to account for the interest rate charge on the cash balance. We quote values for the Greeks consistent with convention, so we quote the deltas and gammas in terms of contracts, multiplying their value by 100 when quoting them. One of my favourite trading stories which I have been unable to verify is that one of the larger trading firms today largely owes its existence to Black Monday in 1987. The answer may seem obvious, but it is not. For a 19 delta call, a contract for 100 shares behaves like it is 19 shares. It depends on the time remaining in the option, and the vol.
To see how this works, we ponder another question. We start with the calculation for the call. Now we are out by a few cents, so our quick calculation is not as good. It will be small, but is important to remember. This provided them with the capital base to grow their operations and they admitted themselves it was pure luck. Options on other instruments also exist: bonds, futures and currencies for example. For ITM options, the intrinsic value of the option is positive, so the price decays to this value at expiration, as we see in the plot. The statement appears to hold.
Thus, the increase in the option price accelerates. Not too bad for a quick calculation! To aid memory, moneyness describes the intrinsic value of the option. There is a lot going on and requires some thinking about why things behave as they do. As option expiration approaches, the distribution of outcomes narrows so Gamma will increase if the option is still close to the strike. We got the price about right, as we did the delta. For the first few sections we hold volatility vol constant: a huge and unrealistic simplification. What is the consequence of this in practical terms? Recall that vol is the standard deviation of the lognormal distribution we assume the price returns are drawn from.
As one final check, let us see what happens if we used a straddle in the above scenario, and then replace the call with the put and stock. Does this have much effect? The theta differences are not surprising as it is the amount of value decay due to time, and it is reasonable for the higher price contract to have a higher theta value: it has more value to decay in the same time period. OTM options also have zero intrinsic value throughout the lifetime, and the underlying has a distance to cross before they are in the money. The new delta and gamma differ also, which must be due to the time effect. USD and the stock is at 95 USD. We have discussed a few times in previous posts the close relationship between the price of a call and put option. In the first instance, with no passage of time, we still had 20 days left in the option. In particular, we discussed how Gamma functions as an accelerator for the option price, magnifying the profit or loss of money of the option due to movements in the share price.
Bear in mind that when trading options, trade sizes are in the hundreds or thousands of contracts. Chicago option floor with no risk. This convention is likely due to both vega and theta being quoted in units of currency. The decay reflects the fact that it takes time for the underlying to move, and so shorter lifetimes reduce the variance of this distribution of prices of the underlying at expiration, in turn reducing the value of the option. In this article we start this exploration, but be warned, we only have time to scratch the surface: there is much more content than we have time for in this series so we will look at a few different things, perhaps suggest a few more avenues of investigation, and try to bring it all together in the fourth and final post of this series. After day 2, the stock has moved up to 100, so what is our PnL? What happens if we relax the time assumption of this move happening over a short period of time? Gamma only moves off zero as the underlying price gets close to the strike. The Gamma of an option is the second derivative of the option price with respect to the price of the underlying.
Is it linear, exponential, something else? We plot the price from 40 days out to expiration, and hold all other inputs constant. If our previous assertion is correct, they are the same. In terms of distributions of possible outcomes, a positive payoff for the option requires us to go further into the right tail as time passes. We will calculate it and see, but before that, it is worth making some educated guesses. We calculate the value of this option over time, using the unrealistic assumption that nothing else will change. Why does the shortened time horizon lead to an increase in gamma?
Is there a point discussing this beyond curiosity? First we looked at how calls and puts are the same from an optionality perspective, then we looked at the effect of time on option premium, in particular how premium erodes as time passes and how the pattern of behaviour in this decay is different depending upon the moneyness of the option. Whilst there are subtle differences between these options that are crucial understanding how to use them, for our purposes here they behave in similar ways. Over small increases, we expect the increase in option value to be larger than that suggested by the delta. Even allowing for interest charges, the discrepancy due to the options being American is narrow enough to be ignored for our purposes. Recall that options are traded as contracts for 100 shares, but are quoted in terms of a single share. Suppose we are 40 days out and the underlying stock is at 95. As a quick exercise, without looking below, will the move in the underlying result in a profit or loss of money in the call and by how much? The delta of the option is positive, so we are long deltas. Those options, which had cost them pennies, ended up being worth 50 or 60 USD each and made the firm millions.
That is a huge change considering the underlying went from 97 to 100. It gives us the instantaneous rate of change of delta as the underlying price changes. USD and so pay interest for one day on this. This is approximate as vega will have a second derivative, but for small changes in vol it is close enough. The put has lost value, but we are also long a share, which has gained in value by 5 USD. The option sustains its value as there is always a large probability of the option expiring in the money right up to expiration. RUT inventory and decided to use the pullback as an opportunity to cut both my delta and upside risk in the trade by taking off the upper put in the BWB and moving it down 10 points. Honestly, it would have been hard for me to time a worse entry. That move took an in the money put and moved it closer to at the money and cut delta.
You can read about that adjustment in this post. That pullback happened the day after I initiated the BWB. In other words, I rolled the long 1260 put down to 1250. RUT continued higher and this time I decided to roll up the initial Butterfly. RUT decided to have a little intraday pullback from around 1230 to 1220. Adjusting an options trade can serve many purposes, but all good adjustments make it more comfortable to stay in the trade and reduce risk. In my mind, those things are always good. RUT trading at 1172. RUT was about to head higher and my location in the trade was, well, bad.
This video goes over some of the reasoning behind adding the BWB. If you have any questions about the trade or the adjustments feel free to post them in the comments below. In other words, rolling down the put allowed me to cut the upside risk in the trade significantly. IWM call to hedge the upside in the trade. RUT springing back to the upside because markets that are trading at all time highs tend to have an upward bias. Lower risk will also make it more comfortable to sit in the position and collect theta as we move closer to expiration.
At this point the trade was under 30 days to expiration and I was becoming a little shorter delta than I wanted.
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