Table 3

Selection of grey forecasting models for forecasting the number of inbound tourists to Iran

Grey forecasting modelsThe reason for selection the model
GM(1,1)The basic grey model, suitable for monotonic trends
RGM(1,1) (Rolling GM(1,1))An extension of GM(1,1) that dynamically updates the model as new data becomes available, improving accuracy in nonstationary time series
Unbiased GM(1,1)Another extension of GM(1,1) that incorporates an unbiased mechanism to enhance forecasting performance
Modified unbiased GM(1,1)A refined version of Unbiased GM(1,1) with additional adjustments to further eliminate bias and enhance forecasting precision
DGM(1,1) (Discrete Grey Model)Represents the discrete version of the grey model, employing a first-order finite difference equation with a single variable
Grey Verhulst ModelDesigned for S-shaped growth patterns, suitable for tourism demand that might exhibit an initial slow growth, followed by rapid expansion, and eventual saturation
Source(s): Ahmadian (2025) 

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