This article investigates growth rates of life insurance companies doing business in New York State between 1860 and 1985. We test the validity ofGibrat's law, which states that the growth rate of an organization is independent of size. We find that Gibrat's law does not hold in this complete organizational population. Rather, growth rates decline as a function of size, supporting the notion that the accrual of organizational inertia reduces the ability of organizations to capitalize on growth opportunities. We also test for an effect of size-localized competition (SLC) on organizational growth rates. Both a standard measure for SLC and an alternative measure that adjusts for population density show that competition between similarly-sized organizations decreases the rate at which organizations grow. Results indicate that the adjusted SLC measure should be used in future research that models first-order density dependence and size-localized competition.