  We address the question of the growth of firm size. To this end, we analyze
the Compustat data base comprising all publicly-traded United States
manufacturing firms within the years 1974-1993. We find that the distribution
of firm sizes remains stable for the 20 years we study, i.e., the mean value
and standard deviation remain approximately constant. We study the distribution
of sizes of the ``new'' companies in each year and find it to be well
approximated by a log-normal. We find (i) the distribution of the logarithm of
the growth rates, for a fixed growth period of one year, and for companies with
approximately the same size $S$ displays an exponential form, and (ii) the
fluctuations in the growth rates -- measured by the width of this distribution
$\sigma_1$ -- scale as a power law with $S$, $\sigma_1\sim S^{-\beta}$. We find
that the exponent $\beta$ takes the same value, within the error bars, for
several measures of the size of a company. In particular, we obtain:
$\beta=0.20\pm0.03$ for sales, $\beta=0.18\pm0.03$ for number of employees,
$\beta=0.18\pm0.03$ for assets, $\beta=0.18\pm0.03$ for cost of goods sold, and
$\beta=0.20\pm0.03$ for property, plant, & equipment.
