The risk-neutral density of is the density of the underlying at under the risk-neutral measure (One Quant Book 4, chapter 5); it is the continuous version of the state prices of chapter 1, divided by the discount factor. The Breeden–Litzenberger formula reads it off call prices:
أمثلة
Example 7.7 (The crash premium)
On the chapter’s surface the three-month forward is 100.37 and the at-the-money volatility 16.36%. With a flat surface at that level the risk-neutral probability that the index ends below 80 is 0.31%; with the skew, whose 80 strike is at 26.8 volatility, it is 1.89%, six times more (Figure 7.4). The 80 put costs 0.006 on the flat surface and 0.219 on the skewed one.