As one would expect from the original Uzawa model, the preference parameters and p both influence the growth rate. A reduction in o or in p, either of which makes people more willing to substitute consumption today for consumption tomorrow, will lead to faster growth. What may be more surprising is that the growth rate does not depend on the size of the labor force L. This result stands in contrast to the implausible result from my earlier paper (Romer 1987) that growth rates are monotonically increasing in L, and it confirms the conjecture that adding human capital as a separate variable and specifying a more reasonable research technology removes the dependence of the growth rate on L. The growth rate also is independent of the parameter that determines the cost in forgone output of producing a unit of a durable. The fact that changes in i do not affect the long run rate of growth of knowledge has implications for policies designed to encourage physical capital accumulation. Like Arrow's model of learning-by-doing (1962a) and my earlier model (Romer, 1986), both of which that tie the rate of growth of A to that of K, this model has the property that A/A is equal to K/K along an equilibrium path. In the earlier models, the ratio of A to K was fixed, so any intervention that increased the accumulation of K also increased the accumulation of A and therefore increased the rate of growth. Here, the ratio of K to A is determined endogenously. If the government offers a subsidy to the accumulation of capital that is financed by a lump sum tax, this has the same effect on growth rates as a reduction in i. (To see a demonstration of this kind of result, see Romer 1989). In the model constructed here, a subsidy will have the effect of increasing the ratio of K to A, but it will not affect the rate of accumulation of A. It therefore will not affect growth rates in the long run.