NBER Working Papers by John McHale

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 remaining innovators access valuable knowledge accumulated abroad (brain bank). We develop a model in which the size of the optimal innovator diaspora depends on the competing strengths of co-location and diaspora effects for accessing knowledge. Then, using patent citation data associated with inventions from India, we estimate the key co-location and diaspora parameters; the net effect of innovator emigration is to harm domestic knowledge access, on average. However, knowledge access conferr...

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 concentration of socially proximate inventors in a city or nation depends on whether spatial and social proximity are complements or substitutes in facilitating knowledge flows. We employ patent citation data, using same-MSA and co-ethnicity as proxies for spatial and social proximity, respectively, to estimate the key KFPF parameters. Although co-location and co-ethnicity both predict knowledge flows, the marginal benefit of co-location is significantly less for co-ethnic inventors. These results imply...

It is well known that patent citations occur disproportionately between patents issued to inventors living in the same location, which has been taken as evidence of geographically localized knowledge spillovers. In this study, we find that patent citations also occur disproportionately often in locations where the cited inventor was living prior to being issued the patent in question, which we interpret as evidence of a significant role played by social capital in promoting knowledge spillovers. We first develop a model of purposeful investments in social capital by co-located inventors that incorporates the effect of expected mobility. Using patent and citation data, we then test two hypotheses motivated by the model. First, we find strong evidence in support of the enduring social capita...

Against a background of projections of sharply increasing elderly dependency rates, workers in the major industrial economies are apprehensive that their social security benefit entitlements will be cut before or after they retire, leaving them with inadequate retirement income. This paper looks at recent benefit rule changes in the G7 countries to see what can be learned about such political risk in PAYG pension systems. From this small sample, I find that projections of rising costs under current rules are inducing reforms, and that these reforms often have a major impact on the present discounted value of promised benefits for middle-aged and younger workers. Usually, however, the benefits of the retired and those nearing retirement are protected. The phasing in of benefit cuts rais...