Own-child estimates of U.S. white fertility, 1886–99

Abstract

The collapse of empires is exceedingly difficult to understand. The author examined the distribution of imperial lifetimes using a data set that spans more than three millennia and found that it conforms to a memoryless exponential distribution in which the rate of collapse of an empire is independent of its age. Comparing this distribution to similar lifetime distributions of other complex systems—specifically, biological species and corporate firms—the author explores the reasons behind their lifetime distributions and how this approach can yield insights into empires.     

The Effects of Data Aggregation in Statistical Analysis

The problem of ecological correlation is now widely recognized but detailed analyses of the effects of aggregation on correlation and regression coefficients are rare. A short review of the aggregation problem is followed by an analysis of the specific effect of proximity aggregation on the slope coefficient of a bivariate linear model using data drawn from the Los Angeles Metropolitan region. The evidence suggests that changes in the slope coefficient are best related to the manner in which the covariation between the independent and dependent variables changes with increased aggregation.     

Palaeoecology and palaeoenvironment of the Jurassic Talbragar Fossil Fish Bed,Gulgong, New South Wales,Australia

BEATTIE, R.G. & AVERY, S., December 2012. Palaeoecology and palaeoenvironment of the Jurassic Talbragar Fossil Fish Bed, Gulgong, New South Wales, Australia. Alcheringa 36, 451–465. ISSN 0311-5518.

The Talbragar Fossil Fish Bed has produced a significant number and variety of insect fossils, including the orders Hemiptera, Coleoptera, Orthoptera, Plecoptera, Odonata, Neuroptera, Diptera, Hymenoptera and Mecoptera. Hemiptera are the most common insects. Coleoptera are both common and diverse. Both orders include terrestrial and aquatic species. The other insect orders represented are less common. Many of the insect fossils discovered were previously unknown in the Australian region during the Jurassic, and the new records extend their palaeogeographic range into southeastern Gondwana. A recent collection of insects, fish, coprolites, gastropods, bivalves, bark, leaves, fruiting bodies, burrows and other ichnofossils supports a model of a shallow-water-lake palaeoenvironment at the northern end of the deposit, grading to a shoreline palaeoenvironment towards the southern end of the deposit. The existence of a productive lake supporting a large population of fish and a diverse, aquatic/shoreline and terrestrial woodland fringe palaeoecosystem, dominated by insects and woody plants, is demonstrated. There is no evidence of tetrapods. The Talbragar Fossil Fish Bed has similarities to Type A and B Mesozoic lake deposits reported from Transbaikalia. Culicimorph pupae are numerous and may have filled a significant niche near the base of the aquatic palaeoecosystem. Other immature aquatic insects are rare. The generally articulated nature of the fossil insects is interpreted to have resulted from a sudden but low-energy burial event.     

Population Suburbanization in American Metropolitan Areas, 1940–1970

Using census tract data, this paper shows that massive changes have occurred in density patterns of American metropolitan areas since 1950. Suburbanization of population has involved both large-scale decongestion of central parts of metropolitan areas and also large-scale outward deconcentration. Many metropolitan areas no longer have clearly distinguishable density patterns in their central and peripheral parts. At the present time, patterns of population distribution across metropolitan areas are becoming increasingly similar. Furthermore, current suburbanization patterns by census tract do not relate strongly to suburbanization patterns as measured by growth rates of crude central city and suburban rings in metropolitan areas. Finally, the paper shows that “density craters” in the center of many metropolitan areas may become more pronounced, although they may not extend outward.     

The micromammalian fauna from Border Cave,Kwazulu, South Africa

The micromammalian fauna from Border Cave is analysed in terms of community composition and structure. Changes in these aspects are interpreted as indicative of changes in vegetation and climate in the vicinity of the cave during the period of deposition. It would appear that vegetation comprised relatively extensive forest or thick bush and dense grass during wetter phases and fairly open savanna woodland, even open grassland, during drier periods. Variation through time in mean mandibular size in two species of Crocidura (musk shrew) was different both in the two species and from what was expected. It now seems likely that the size change constitutes a response to complex phenomena and not simply to changes in temperature. Comparison with the Boomplaas A sequence indicates that the same general pattern of change is reflected at both sites but that there was a greater amplitude of change at Boomplaas A and that ¹⁸O stage 4 was dry at this site but wet at Border Cave. Evidence for periodic changes in the distribution of various species, and in some cases the mutually exclusive occurrence of ecologically equivalent species, has implications for the zoogeography of the species involved. In particular, the occurrence of Pelomys fallax (creek rat) in the lower half of the sequence is of interest in view of its present distribution 600 + km north of Border Cave.