Background I want to look at this FX rate with the risk-neutral measure. I read that we strip away the real-world historical trend ( ). In the risk-neutral world, my assumption is that investors do not demand a risk premium for holding volatile assets, which means the expected return on any asset must equal the risk-free rate. My attempt For FX, the solution with is governed by Garman-Kohlhagen framework (the FX extension of Black-Scholes). where: is the exchange rate (how many USD per 1 EUR). is the domestic interest rate (USD rate, since USD is the pricing currency). is the foreign interest rate (EUR rate, acting exactly like a continuous dividend yield in the classic Black-Scholes formula. Applying Itô's Lemma under the measure gives the exact solution for the exchange rate at time : To see how this differs from the real-world calculation, let's look at the risk-neutral expected value, which is used directly to calculate forward rates and price options: Current Rate ( ): . US Interest Rate ( ): let's assume a standard risk-free rate of ( ). Eurozone Interest Rate ( ): let's assume the European Central Bank rate is at ( ). Time ( ): year. \begin{align*} E^{\mathbb{Q}}[X_T] &= 1.14376 \cdot e^{(0.045 - 0.0325) \cdot 1}\ &= 1.14376 \cdot e^{0.0125}\ &= 1.14376 \cdot 1.01258\ &= \boxed{1.1581} \end{align*} My questions Would this be correct? Also, do quants/analysts typically separate the entire financial universe into two distinct domains: the -World (Risk-Neutral)? and, the -World (Physical/Real-World)? So, if we are market-making options traders or a derivatives pricing quants, we'd work exclusively with (Risk-Neutral Measure)? If we are risk managers or a directional algorithmic traders, we would use without ( -Measure)? Also, to find the explicit solution to this SDE without using , we apply Itô's Lemma directly to the real-world process. The exact solution for the exchange rate at a future time is: Current Rate ( ): Real-World Annual Drift ( ): (from the 1-year return on the screen) Annual FX Volatility ( ): let's assume a standard ( ) for G10 currencies. Time ( ): year If we want to find the expected mathematical baseline for the exchange rate next year without pricing options, we take the expected value \begin{align*} E^{\mathbb{P}}[X_T] &= X_0 e^{\mu T}\ &= 1.14376 \cdot e^{-0.0288 \cdot 1}\ &= 1.14376 \cdot 0.9716\ & = \boxed{1.1113} \end{align*} As such?

$\mathbb{P}$ vs. $\mathbb{Q}$ measure in FX options
Jessie

