In the base case, nine trading days to expiry with the announcement at day 4.5, the one scheduled jump carries 86 percent of the variance of the log price at expiry.
On the known announcement date the price moves once by a double-exponential log return, shifted by its compensator.
- the announcement date, known in advance: day 4.5 of 9 in the base case
- the price just before the announcement
- the announcement log return, drawn once
- its log compensator, 0.00696867 in the base case
- the double-exponential law: up-move probability and the two tail rates, DE(0.5, 12, 12) in the base case
A seeded simulation (seed 20261015) of 48 price paths under the model, starting at 100 and running 9.0 trading days with the announcement at 4.5 days. At the announcement every path jumps at once: 21 move up and 27 move down, and the standard deviation of the announcement log moves across the paths is 0.1040. At expiry the standard deviation of ln(S_T / S_0) across the paths is 0.1155.
Fig. H3. Simulated paths of the model under the pricing measure, seed 20261015, with the announcement jump at day 4.5.
Supporting Equations · The Dynamics
Kou dynamics between announcements
Martingale condition across the announcement
Compensator of the Poisson jumps
The shift is the logarithm of the expected price multiplier, in closed form from the three parameters of the announcement law.
- the expected price multiplier of the announcement
- 0.0833 in the base case, a standard deviation of 0.1179
- 0.013889 of a total 0.016121 for the log price at expiry: 86 percent
The announcement jump's double-exponential density on log returns, f_E(z) = p eta1 exp(-eta1 z) for z at least 0 and (1 - p) eta2 exp(eta2 z) below 0, drawn as a solid of revolution whose radius at each z is the density there. Here p = 0.50, eta1 = 12.00, and eta2 = 12.00: the mean up-move is 0.083 and the mean down-move 0.083 in log return, E|Z| = 0.0833, the standard deviation is 0.1179, and the compensator kappa_E = ln E[exp Z] = 0.00697.
Fig. H2. Double-exponential density of the announcement log return, DE(0.5, 12, 12). The solid revolves the density about the z axis: its radius at each log return is the density there.
Supporting Equations · The Jump Law