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The theory of the marginal consumer holds that a subset of better informed consumers can create a globally more efficient market through their purchase decisions. In the market for education created by recent school choice initiatives, these "market mavens" are essential to the successful functioning of the choice system given the empirically documented low quantity and quality of information possessed by the average consumer. Little is known, however, about the differences between how marginal consumers and average consumers of education search for information and make decisions about their children's schooling.  相似文献   
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Previous analyses of the Emeryville Shellmound fauna suggested that ever-expanding late Holocene human populations of the San Francisco Bay area depressed a wide range of vertebrate taxa, including cormorants (Phalacrocorax), geese (Anserinae), and large shorebirds (e.g., Numenius, Limosa). Far-reaching implications for prehistoric human behavior, historical ecology, and modern conservation biology have resulted from that work. We test the generality of the bird-based conclusions here by documenting temporal trends in avifaunal abundances from five additional sites located on the San Francisco Peninsula. Analyses of these data reveal patterns identical to those found at Emeryville, showing significant declines through time in the relative abundances of both geese and cormorants between about 2000 and 700 B.P. New photon absorptiometric-based density data for cormorants, geese, and ducks (Anatinae) are used to determine if the declines through time in the relative abundances of geese and cormorants are correlated with variation in the extent of density-mediated attrition observed in these faunas. The data and analyses presented here suggest that while density-mediated attrition played a role in structuring element abundances in these avifaunas, there is no evidence that it varied systematically through time to produce the revealed patterns in taxonomic abundances. Resource depression thus remains a viable hypothesis for the declining abundances of large-sized waterbirds during the late Holocene of the San Francisco Bay region. The new bone density data we present should be useful to analyses of archaeological and paleontological avifaunas wherever these or related taxa are found around the world.  相似文献   
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JELL, P.A., WOODS, J.T. & COOK, A.G., May 2017. Mecochirus Germar (Decapoda: Glypheoidea) in the Lower Cretaceous of Queensland. Alcheringa 41, 514–523 ISSN 0311-5518.

Three new species of glypheoid decapod crustaceans, Mecochirus mcclymontorum, M. bartholomaii and M. lanceolatus, are described from the late Aptian of the Eromanga, Carpentaria and Maryborough basins, respectively. The first two occur in the Doncaster Member of the Wallumbilla Formation and the last in the Maryborough Formation. This is the first record of Mecochirus Germar, 1827 or the Mecochiridae Van Straelen, 1925 in Australia and one of only a few Cretaceous occurrences of this largely Jurassic genus.

Peter A. Jell [], Jack T. Woods and Alex G. Cook [], School of Earth Sciences, The University of Queensland, St Lucia Queensland 4072, Australia.  相似文献   

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