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Problem 325 of 333MediumStochastic CalculusP325
How often does a trend follower lose?
An asset's price, measured in price units from where it starts, is for , where is a standard Brownian motion. A trend follower holds units at time : long when the price is above its starting level, short when it is below, rebalancing continuously. Each position is set before the next price move, so the P&L is the Itô integral
(a) Write in terms of alone, and find as a function of .
(b) Take . What is the probability that the strategy loses money? What is the largest possible loss? What are the average loss given a loss and the average gain given a gain?
(c) Now the asset trends, with or . What are and the probability of a loss?
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