Forecast of Freight Volume in Xi’an Based on Gray GM (1, 1) Model and Markov Forecasting Model

Table 5

Predicted value comparison between the Gray GM (1, 1) model and Gray–Markov model.

Year	Gray predicted value ()	Relative error (%)	Gray–Markov predicted value ()	Relative error (%)
2009	2.6050	−14.89	2.6106	−14.70
2010	3.0894	−9.99	3.0956	−9.81
2011	3.6325	−7.43	3.6708	−6.45
2012	4.3272	−3.68	4.3528	−3.11
2013	5.1615	2.98	5.1449	2.65