Workers in high-tech cities earn raw wages that are on average 17% higher than wages of workers in other cities. Using a large sample from the 5% PUMS of the 2000 Census of Population, this paper presents econometric evidence of a 'tech-city wage premium' of approximately 4.6% that is not the result of higher-ability people self-selecting to live in high-tech cities, but rather the result of high-tech cities actually making workers more productive. Although knowledge spillovers are difficult to assess, we use the concepts of the new economic geography and evidence from empirical studies of high-technology regions, such as Silicon Valley and Austin, Texas, to support the view that workers who live in high-tech cities might be more productive because they benefit from a larger supply of knowledge spillovers than workers who live in low-tech cities. Copyright (c) 2008 the author(s). Journal compilation (c) 2008 RSAI.

The Galapagos sea lion ( Zalophus wollebaeki ), an endangered species, experiences high pup mortality (up to 100%) in years when El Niño events reduce food supply in the Galapagos Islands. Mortality of pups in non-El Niño years is estimated to be 5% in undisturbed colonies. From 2009 to 2012 we observed high pup mortality (up to 67%) in colonies close to the Galapagos capital, Puerto Baquerizo Moreno, where contact with humans, domestic animals, and rats is frequent. Gross postmortem findings from 54 pups included hemorrhagic lesions in liver and congestion in lungs; histopathology suggested a possible association with infectious diseases. Evidence of Leptospira infection was found in five out of seven samples collected in 2010. Canine distemper viral (CDV) RNA was detected in tissues from six sea lions (in 2011-12), four of which were confirmed by nucleotide sequencing. The absence of CDV antibodies in 109 juvenile animals tested in 2014 at urban and remote colonies could indicate that the CDV infection observed in 2011 was likely confined to a few animals. Our results indicated that Galapagos sea lions have been exposed at least to two pathogens, Leptospira and CDV; however, the impact of these infections on the sea lions is unclear.

The literature on the relationship between city size and urban wages argues that productivity and wages are higher in larger cities. Indeed, a doubling of city size is associated with a 4-8 per cent increase in wages. The human capital externalities literature finds evidence of higher wages in cities with an abundant supply of human capital where knowledge spillovers are plentiful. Interestingly, cities with a large supply of human capital are not themselves large. They have a population of fewer than 1.5 million inhabitants. In view of this evidence, this paper questions whether city size has lost its importance as a determinant of high wages. In other words, is city size necessary to explain wage variations, after controlling for knowledge spillovers? Using a large sample from the 5 per cent PUMS of the 2000 US Census, this paper presents econometric evidence for city size and learning spillover effects on productivity.

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