The proposed models were built by using Fourier series to modify their residual values. To verify the effectiveness of these proposed models, the international tourism demand in Vietnam from Jan 2005 to Feb 2015 is used for the modeling to forecast the international tourism demand from Mar 2015 to May 2015, and the forecasting results proved that the FRMGM (1, 1) is a better model in forecast the international tourism demand in Vietnam. | Hue University Journal of Science ISSN 1859-1388 Vol. 113, No. 14, 2015, pp. 157-167 ENHANCED PREDICTION ACCURACY OF GREY FORECASTING MODEL: A CASE BY TOURISM INDUSTRY IN VIETNAM Phan Van Thanh* Quang Binh Univerisity Abstract: grey forecasting based on the grey system theory is a diverse forecasting model and has been successfully applied in various fields. In recent years, many scholars have proposed new procedures or new models with different ways to improve the prediction accuracy of grey forecasting for fluctuating data sets. However, the prediction accuracy of the existing grey forecasting models may not be always satisfactory in different scenarios. For example, the data not only consist of trend, seasons but highly fluctuate with lots of noise as well. To overcome this drawback, this paper proposed two effective combined grey models, namely Fourier grey Model (1, 1) (abbreviated as F-GM (1, 1)) and Fourier Nonlinear grey Bernoulli Model (abbreviated as F-NGBM (1, 1). Two proposed models were built by using Fourier series to modify their residual values. To verify their performance and effectiveness, these proposed models were used to forecast the international tourism demand in Vietnam from Jan. 2006 to Mar. 2016. The empirical results demonstrated that the accuracy of both GM (1, 1) and NGBM (1, 1) forecasting models after using Fourier series to revise their residual error provided more accuracy than original ones in terms of insample and out-of-sample cases. Further more, this paper also indicated that the F-GM (1, 1) is the better model than other forecasting models in forecasting the international tourist arrival to Vietnam with average MAPE of in-sample and out-of-sample of and %, respectively. Keywords: grey system theory, GM (1, 1), NGBM (1, 1), Fourier series, International tourism demand 1 Introduction Grey system theory established during the 1980s by Deng [12] is a quantitative method dealing with grey systems that are .
