This paper argues that the theoretical foundations for the gravity equation are general, while the empirical performance of the gravity equation is specific to the type of goods examined. Most existing theory for the gravity equation depends on the assumption of differentiated goods. We show...

In this paper we examine how to account for growth when new inputs are being created. In particular, we obtain a decomposition of growth into that due to a higher quantity of existing inputs, and that due to a greater range of inputs. This decomposition is first obtained for a single firm, with...

In this paper we examine how to account for growth when new inputs are being created. In particular, we obtain a decomposition of growth into that due to a higher quantity of existing inputs, and that due to a greater range of inputs. This decomposition is first obtained for a single firm, with...