The development prospects of a poor country depend in part on its capacity for innovation. The productivity of its innovators depends in turn on their access to technological knowledge. The emigration of highly skilled individuals weakens local knowledge networks (brain drain), but may also help...

We examine how the spatial and social proximity of inventors affects knowledge flows, focusing especially on how the two forms of proximity interact. We develop a knowledge flow production function (KFPF) as a flexible tool for modeling access to knowledge and show that the optimal spatial...