ILR Impact Brief - Industry Clusters Affect Job Mobility and Earnings Growth

[Excerpt] Industry clusters are associated with greater job hopping and faster growth in workers’ earning power relative to the experience of workers at less spatially concentrated companies. Workers in these clusters tend to accept lower starting salaries than peers at more isolated firms in anticipation of rapid gains that accompany movement from job to job within the cluster and the accumulation of industry-specific knowledge. Higher earnings observed among workers in clustered firms may also reflect choices made by workers with certain characteristics to seek employment in an area with a high concentration of similar firms and by companies with certain characteristics to locate in such an area

America's earliest economic development initiatives provide perspective on recent battles over jobs.

Government efforts to attract businesses using tax incentives and other subsidies are nothing new in the United States. Matthew Freedman writes about Mississippi's "Balance Agriculture with Industry" Program, which endeavored to attract manufacturing operations to the state using taxpayer dollars in the 1930s. Mississippi's program shares features with many modern-day economic development initiatives, though its short- and long-run impacts on ..

Teaching New Markets Old Tricks: The Effects of Subsidized Investment on Low-Income Neighborhoods

This paper examines the effects of investment subsidized by the federal government’s New Markets Tax Credit (NMTC) program, which provides tax incentives to encourage private investment in low-income neighborhoods. I identify the impacts of the program by taking advantage of a discontinuity in the rule determining the eligibility of census tracts for NMTC-subsidized investment. Using this discontinuity as a source of quasi-experimental variation in commercial development across tracts, I find that subsidized investment has modest positive effects on neighborhood conditions in low-income communities. Though spillovers appear to be small and crowd out incomplete, the results suggest that some of the observed impacts on neighborhoods are attributable to changes in the composition of residents as opposed to improvements in the welfare of existing residents

Distribution and Impacts of Invasive Bivalve Corbicula fluminea in Tidal Freshwater York River Tributaries

The Asian clam, Corbicula fluminea, is one of the most invasive bivalves in the world but there is limited research on its presence in tidal freshwater systems. Despite its introduction into Chesapeake Bay tributaries in the 1970s, the initial colonization and subsequent development of populations of C. fluminea in the Mattaponi and Pamunkey sub-tributaries of the York River, Virginia, is mostly undocumented. This study assessed the spatial distribution and population structure of C. fluminea in tidal freshwater sections of these rivers (~45km) with benthic surveys during summer 2011 – 2012. Benthic grabs (2.4L, 0.023m2) taken at 40 sites in each river were analyzed for clam abundance and size. In addition, relationships between abiotic factors and clam distribution within each river were evaluated using Akaike’s Information Criterion (AIC) to compare a set of generalized linear models. C. fluminea was present at the majority of sites in both rivers during both years, with mean densities (m-2) during 2011 and 2012 of 660 and 410 for Mattaponi River; 1,451 and 834 for Pamunkey River. Populations were dominated by \u3e 90% juvenile clams (\u3c 6mm shell length), which is common for C. fluminea populations during recruitment periods. Both rivers had lower abundance during 2012, suggesting that C. fluminea is actively reproducing but not necessarily accumulating in the system. High juvenile and adult mortality are characteristic of C. fluminea populations. Compared to other invaded systems, C. fluminea in Mattaponi and Pamunkey Rivers is a low-to-moderate level invasion based on clam density. Using AIC analysis, the bestsupported models included factors of distance upriver (km), % sand, depth (m), and year. Distance and % sand showed positive relationships with C. fluminea abundance and had significant parameter estimates in all models ( = 0.05). Spatial analysis in GIS showed 3 that C. fluminea was widely distributed throughout the rivers but achieved higher densities further upriver and in sandier habitats. Despite these trends, Corbicula densities were highly variable, highlighting eurytopic habitat preferences of this species that have led to its successful invasion of tidal freshwater habitats. Populations may also be controlled by the high degree of physical disturbance in tidal freshwater systems and predation by fish and waterfowl

Knot Floer homology of Whitehead doubles

In this paper we study the knot Floer homology invariants of the twisted and untwisted Whitehead doubles of an arbitrary knot K. We present a formula for the filtered chain homotopy type of HFK(D(+,K,t)) in terms of the invariants for K, where D(+,K,t) denotes the t-twisted positive-clasped Whitehead double of K. In particular, the formula can be used iteratively and can be used to compute the Floer homology of manifolds obtained by surgery on Whitehead doubles. An immediate corollary is that tau(D(+,K,t))=1 if t< 2tau(K) and zero otherwise, where tau is the Ozsv{\'a}th-Szab{\'o} concordance invariant. It follows that the iterated untwisted Whitehead doubles of a knot satisfying tau(K)>0 are not smoothly slice.Comment: 41 pages, 14 color figures. spelling errors corrected and other minor change