Prediction of China’s Sulfur Dioxide Emissions by Discrete Grey Model with Fractional Order Generation Operators

Table 4

The forecast values and errors of different discrete grey models (year 2009).

Model
Forecast value (unit: billion tons-km)	5236.45	5303.33	5585.60	5185.92
Absolute percentage error (%)	1.59	2.89	8.36	0.61