Before revision:  By theoretical analysis, we obtain the mean-field solution of money-transport models and find thatthe scaling exponent can be determined from the  average degree of the nearest neighbours , which is one of the cardinal features of a network .
After revision:  By theoretical analysis, we obtain the mean-field solution of the model and found that, in the case of the Japanese firms, the scaling exponent of 1.3 can be determined from the average degree of the nearest neighbours , which is one of the cardinal features of a network .