Double Exponential Smoothing

Crystal Ball uses Holt’s double exponential smoothing formula as follows:

(Initialization) L₁ = Y₁, T₁ = 0

Level: L_t = α * Y_t + (1 – α) * (L_t-1 + T_t-1)

Trend: T_t = β * (L_t – L_t-1) + (1 – β) * T_t-1

Fit: F_t = α * Y_t-1 + (1 – α) * F_t-1

Forecast for period m: F_t+m = L_t + m*T_t

Note:

First fit is available from period 2.