  We study the growth dynamics of the size of manufacturing firms considering
competition and normal distribution of competency. We start with the fact that
all components of the system struggle with each other for growth as happened in
real competitive bussiness world. The detailed quantitative agreement of the
theory with empirical results of firms growth based on a large economic
database spanning over 20 years is good .Further we find that this basic law of
competition leads approximately a power law scaling over a wide range of
parameters. The empirical datas are in accordance with present theory rather
than a simple power law.
