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Quantitative Finance · Glosario

¿Qué es Implied–realised spread?

También llamado: implied--realised spread

Definition 25.2 Derivatives and Volatility · Capítulo 25 — Trading Volatility

The implied–realised spread of an option position is the difference between the implied volatility at which it was traded and the volatility subsequently realised by the underlying over its life, the quantity a delta-hedged position is a bet on, and only on average.

A one-month straddle bought at 18 volatility and hedged daily along three paths that all realise 25%. Left: the share (dotted: the strike). Right: the cumulative P&L. On the wrong days the share leaves the strike quietly and moves wildly where the straddle has no gamma left. Data: the tutorial.
Figure 25.1. A one-month straddle bought at 18 volatility and hedged daily along three paths that all realise 25%. Left: the share (dotted: the strike). Right: the cumulative P&L. On the wrong days the share leaves the strike quietly and moves wildly where the straddle has no gamma left. Data: the tutorial.

Ejemplos

Example 25.3 (Same volatility, different days)

A 21-day at-the-money straddle on a share at 100, bought at 18 volatility (premium 4.15), hedged daily at 18. Three paths all realise exactly 25%:

  • even: a move of ±1.57%\pm1.57\% every day, up and down in turn. The straddle makes 3.28;
  • the wrong days: fifteen days of +0.5%+0.5\% (7.9% realised), which take the share to 107.8, then six days of ±2.84%\pm2.84\% (45% realised). The quiet weeks lose 0.80 while the gamma is large; the wild week, far from the strike, makes 0.02. The total is −0.78-0.78;
  • the right days: fifteen days of ±0.5%\pm0.5\% at the strike, then the same wild week there, with the most gamma of the month. The straddle makes 2.87.

The cash-gamma sum reproduces these within a few tenths (3.05, −0.86-0.86, 3.03): the rest is the higher-order terms of the large moves (Figure 25.1).

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