S&P 500 Short Straddle Still Hugging 1000 Level

By Bill Luby on September 4, 2009 | More Posts By Bill Luby | Author's Website

In many respects the ultimate pure play on declining volatility is a short straddle in which near the money puts and calls are sold simultaneously in hopes that the underlying will move very little prior to expiration. While this is largely a neutral directional bet, it is also a bet on declining volatility.Two weeks ago today, in The Sideways Play, I outlined some of the logic and details behind what a short straddle trade would look like with the S&P 500 (SPX) (^GSPC: 1003.24 0.00 0.00%) at 1004. Two weeks later, with the SPX down a little more than five points, this trade is a winner. This trade is profiting from time decay (theta), which is currently at -1.20, meaning that all else being equal (i.e., if price, implied volatility and interest rates do not change), the position will gain $120 per day.

Of course, the other variables that affect the price of an option are in motion as well. Options traders use options Greeks to measure an option’s sensitivity to various influences on the value of that option, including the price of the underlying, the volatility of the underlying, time and interest rates.Specific to the SPX short straddle, the increase in implied volatility (^VIX: 27.10 0.00 0.00%) over the course of the past few days has worked against the options position. The Greek which measures an option’s sensitivity to changes in implied volatility is vega (not a Greek letter, but one that is counted as a ‘Greek’ according to options tradition), which estimates the change in value of an option that would result from a 1% change in the implied volatility of the underlying. In the two weeks, the VIX has increased 2.30 points and as the SPX straddle currently has a vega of 1.61, this means that the 2.30 point rise in the VIX has cost the position approximately $370 during the ten trading days.

While there are other factors at work on this short straddle trade, so far the main plot line has been a story of theta vs. vega, with time decay winning out.
The graphic below shows that a position which originally yielded $5000 in premium can now be bought back for $3510, which would lock in a profit of $1490. With the options expiring two weeks from tomorrow and time decay beginning to accelerate as we approach expiration, it will be interesting to see how this short straddle plays out.