Job-Hopping in Silicon Valley: Some Evidence Concerning the Micro-Foundations of a High Technology Cluster

Observers of Silicon Valley’s computer cluster report that employees move rapidly between competing firms, but evidence supporting this claim is scarce. Job-hopping is important in computer clusters because it facilitates the reallocation of talent and resources toward firms with superior innovations. Using new data on labor mobility, we find higher rates of job-hopping for college-educated men in Silicon Valley’s computer industry than in computer clusters located out of the state. Mobility rates in other California computer clusters are similar to Silicon Valley’s, suggesting some role for features of California law that make non-compete agreements unenforceable. Consistent with our model of innovation, mobility rates outside of computer industries are no higher in California than elsewhere.agglomerations, clusters, non-compete agreements, human capital, innovation, Silicon Valley, modular production.

"Job-Hopping in Silicon Valley: Some Evidence Concerning the Micro-Foundations of a High Technology Cluster"

Observers of Silicon Valley's computer cluster report that employees move rapidly between competing firms, but evidence supporting this claim is scarce. Job-hopping is important in computer clusters because it facilitates the reallocation of talent and resources toward firms with superior innovations. Using new data on labor mobility, we find higher rates of job-hopping for college-educated men in Silicon Valley's computer industry than in computer clusters located out of the state. Mobility rates in other California computer clusters are similar to Silicon Valley's, suggesting some role for features of California law that make non-compete agreements unenforceable. Consistent with our model of innovation, mobility rates outside of computer industries are no higher in California than elsewhere.

The Palaeoproterozoic global carbon cycle : insights from the Loch Maree Group, NW Scotland

Fieldwork was supported by the Edinburgh Geological Society Clough & Mykura Fund, the Carnegie Undergraduate Scholarship and a stipend provided by the Irvine Bequest through the University of St Andrews to G.B.K. Laboratory work, and isotope and geochronology analyses were financed by NERC grant NE/G00398X/1 to A.R.P., A.E.F., D.J.Condon and A.P.M. Thanks go to T. Donnelly, J. Dougans, A. Calder, D. Herd, B. Pooley and A. Mackie for laboratory assistance.Peer reviewedPostprin

Heterogeneous Agglomeration

Many prior treatments of agglomeration explicitly or implicitly assume that all industries agglomerate for the same reasons. This paper uses U.K. establishment-level coagglomeration data to document substantial heterogeneity across industries in the microfoundations of agglomeration economies. It finds robust evidence of organizational and adaptive agglomeration forces as discussed by Chinitz (1961), Vernon (1960), and Jacobs (1969). These forces interact with the traditional Marshallian (1890) factors of input sharing, labor pooling, and knowledge spillovers, establishing a previously unrecognized complementarity between the approaches of Marshall and Jacobs, as well as others, to the analysis of agglomeration

A demonstration of an affinity between pyrite and organic matter in a hydrothermal setting

One of the key-principles of the iron-sulphur world theory is to bring organic molecules close enough to interact with each other, using the surface of pyrite as a substrate in a hydrothermal setting. The present paper explores the relationship of pyrite and organic matter in a hydrothermal setting from the geological record; in hydrothermal calcite veins from Carboniferous limestones in central Ireland. Here, the organic matter is accumulated as coatings around, and through, pyrite grains. Most of the pyrite grains are euhedral-subhedral crystals, ranging in size from ca 0.1-0.5 mm in diameter, and they are scattered throughout the matrix of the vein calcite. The organic matter was deposited from a hydrothermal fluid at a temperature of at least 200°C, and gives a Raman signature of disordered carbon. This study points to an example from a hydrothermal setting in the geological record, demonstrating that pyrite can have a high potential for the concentration and accumulation of organic materials

Long term geological record of a global deep subsurface microbial habitat in sand injection complexes

Peer reviewedPublisher PD

The laurentian record of neoproterozoic glaciation, tectonism, and eukaryotic evolution in Death Vally, California

Neoproterozoic strata in Death Valley, California contain eukaryotic microfossils and glacial deposits that have been used to assess the severity of putative Snowball Earth events and the biological response to extreme environmental change. These successions also contain evidence for syn-sedimentary faulting that has been related to the rifting of Rodinia, and in turn the tectonic context of the onset of Snowball Earth. These interpretations hinge on local geological relationships and both regional and global stratigraphic correlations. Here we present new geological mapping, measured stratigraphic sections, carbon and strontium isotope chemostratigraphy, and micropaleontology from the Neoproterozoic glacial deposits and bounding strata in Death Valley. These new data enable us to refine regional correlations both across Death Valley and throughout Laurentia, and construct a new age model for glaciogenic strata and microfossil assemblages. Particularly, our remapping of the Kingston Peak Formation in the Saddle Peak Hills and near the type locality shows for the first time that glacial deposits of both the Marinoan and Sturtian glaciations can be distinguished in southeastern Death Valley, and that beds containing vase-shaped microfossils are slump blocks derived from the underlying strata. These slump blocks are associated with multiple overlapping unconformities that developed during syn-sedimentary faulting, which is a common feature of Cyrogenian strata along the margin of Laurentia from California to Alaska. With these data, we conclude that all of the microfossils that have been described to date in Neoproterozoic strata of Death Valley predate the glaciations and do not bear on the severity, extent or duration of Neoproterozoic Snowball Earth events