  We present a novel approximation method that can predict the number of
solitons asymptotically appearing under arbitrary rapidly decreasing initial
wave packets. The number of solitons can be estimated without integration of
the original soliton equations. As an example, we take the one-dimensional
nonlinear Schrodinger equation and estimate the behaviors of the scattering
amplitude in detail. The results show good agreement compared with those
obtained by direct numerical integration. The presented method is applicable to
a wide class of one-dimensional soliton equations.
