Abstract: In recent years, experience economy characterized by customer-oriented has become the mainstream economic form. The word of mouth(WOM) which reflects the product experience has been more and more important for new product diffusion(NPD). The NPD research needs to be adapted to the development of management situation. It is essential to stress the influence of WOM on NPD, and to make full use of WOM to improve the prediction performance. The existing research neglects the synergistic effect of positive and negative WOM and the application in market demand prediction. Therefore, WOM is introduced into the classic Bass model, the model is extended from two points of quantity and proportion adjusting effect, and the NPD model is established on two WOM effects, called DBM. Moreover, the properties of the solution are analyzed and the main law of NPD on two WOM effects is found. Based on it, 65 American movies between 2010 and 2014 including 42 nominations of Oscar Best Picture and 23 nominations of Golden Raspberry Award are chosen to make empirical analysis.
The main research conclusion includes the following three aspects:firstly, quantity and proportion effect are two main effects of WOM on NPD. Quantity effect means that interest group affected by adoption group become a dynamic process. And proportion effect refers to the different degree of imitation effect of the buyers with positive and negative WOM, which influences the probability of purchasing decisions of potential groups. Secondly, the properties of the solution are analyzed and it is found that when net flow of interest groups and proportion of negative WOM increase, the peak time turns shorter and peak sales, cumulative sales at peak time and total sales become larger. But if the imitate effect is much more than innovation effect, the proportion of negative WOM is higher, the attenuation of NPD will get slower. Thirdly, the empirical results suggest that the improved model has better fitting and forecasting performance than the classical model.
The meaning of this study includes the following three aspects:firstly, introducing WOM into the classic Bass model, we reshape the NPD process. Classic Bass model neglects the lost demand problem caused by negative WOM. The group flow process like "potential groups-interest group-adoption group-group with positive and negative WOM", which enhances the understanding of synergy effect of positive and negative WOM, is pointed out. Secondly, the new product diffusion model on two adjusting effects is established, the analytical solution is solved and the theoretical proof of the correlation between double WOM effect and NPD is given. Thirdly, based on WOM data, the NPD forecasting can reflect the consumer experience trend. Enterprises can then formulate the corresponding consumer experience promotion strategy and marketing strategy.

Key words: new product diffusion, Bass model, word of mouth, quantity effect, proportion effect