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Black & Scholes : Rhô ρ
Issued on September 13 2011 par Strategies-options.com

Rho, like vega, doesn't exist in the Black & Scholes Model.
Interest rate is a part of what makes option prices.

The sensitivity of an option value to an interest rate variation is certainly one of the less known Greeks, and the less understood.



I - Black & Scholes Rho

If we get :
Variables
t the starting date
S the spot

Parameters
K the strike
r continuously compounded annualized interest rate
q continuously compounded annualized dividend rate
T expiry (in years)
σ the annualized volatility

For a maturity of τ = T - t ,


ρ = ∂ C / ∂ r
ρ = ∂ [ exp ( - q.τ ) . S . N( d1 ) - exp ( - r.τ ) . K . N( d2 )] / ∂ r
ρ = K . ( τ ) . exp( - r .τ ) . N(d2)

ρ = ∂ P / ∂ r
ρ = ∂ [ - exp ( - q.τ ) . S . N( - d1 ) + exp ( - r.τ ) . K . N( - d2 )] / ∂ r
ρ = - K . ( τ ) . exp( - r .τ ) . N( - d2)


With
d1 = [ Ln( S/K ) + ( ( r-q + 0.5σ² ).τ )] / ( σ√τ )
d2 = [ Ln( S/K ) + ( ( r-q - 0.5σ² ).τ )] / ( σ√τ ) = d1 - ( σ√τ )
N(.) Cumulative Normal Denstity
N( d1 ) = ∫ [ ((1 / ( √2п )) . exp( -z²/2 ) ] dz, derived between –inf and d1



II - Graphs






Next : Black & Scholes: Let's Price With It !
Previous : Black & Scholes : Vega υ


Related Pdf :

- Understanding N(d1) and N(d2) : Risk-Adjusted Probabilities in the Black-Scholes Model
- Black-Scholes Option Pricing Model


OPTIONS PRICING MODEL - INDEX
OPTIONS PRICING MODEL - INDEX
OPTIONS PRICING MODEL - CHAPTER I
OPTIONS PRICING MODEL - CHAPTER II
OPTIONS PRICING MODEL - CHAPTER III

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