Cross-sectoral effects of retailing firm demographies

With regard to the interrelationship between firm births and deaths, Johnson & Parker (1994, 1996) have summarized the various causality relationships into three different effects: what they call the Multiplier, the Competition and the Marshall effects. In a recent paper, Dejardin (2001) has built on these earlier contributions and has suggested an enlarged analytical framework by introducing and discussing (inter)sectoral and spatial dimensions. Multiplier and Competition effects were reassessed according to the degree of sectoral disaggregation and to Hicks & Allen (1934) complementarity between economic activities. We suggested that the Competition (Multiplier) effect should overcome more probably the Multiplier (Competition) effect since analyses and empirical studies are focused on very disaggregated (aggregated) sectoral demographic events. Preliminary spatial econometric results obtained for Belgian retailing industries confirmed the relevance of an (inter)sectoral and spatial setting for research in the interrelationship between firm births and deaths. Estimates relate to 16 retailing industries and their aggregate. However, this previous research encounters various limitations. So, from a theoretical point of view, it appears that arguments already exposed could be more explicit, as we referred to general analytical framework such as Hicks & Allen notion of complementary goods or spatial oligopolistic models that were only very briefly discussed. From an empirical point of view, data were exploited through the estimations of an econometric model which specification may reveal heavy without meaning important gains in terms of econometric accuracy or explanatory efficiency. The aims of this new paper are mainly to respond to these limitations and to give a more emphatic treatment of cross-sectoral effects. Concerning this last and more specific purpose, we test different sectoral matchings (or aggregations) and interpret the new econometric results that are obtained through this more flexible and a priori less defined statistical treatment. References DEJARDIN, M. (2001), "Firm demography in a sectoral and spatial setting", paper presented at the Third Congress on Proximity 'New Growth and Territories', Paris, December 13-14. JOHNSON, P. & S. PARKER (1994), "The interrelationships between births and deaths", Small Business Economics, 6, 283-290. JOHNSON, P. & S. PARKER (1996), "Spatial variations in the determinants and effects of firm births and deaths", Regional Studies, 30, 7, 679-688. HICKS, J. & R. ALLEN (1934, "A reconsideration of the theory of value, parts I and II", Economica, N.S., February, pp. 52-76 and May, pp. 196-219.

Cross-sectoral effects of retailing firm demographies

With regard to the interrelationship between firm births and deaths, Johnson & Parker (1994, 1996) have summarized the various causality relationships into three different effects: what they call the Multiplier, the Competition and the Marshall effects. In a recent paper, Dejardin (2001) has built on these earlier contributions and has suggested an enlarged analytical framework by introducing and discussing (inter)sectoral and spatial dimensions. Multiplier and Competition effects were reassessed according to the degree of sectoral disaggregation and to Hicks & Allen (1934) complementarity between economic activities. We suggested that the Competition (Multiplier) effect should overcome more probably the Multiplier (Competition) effect since analyses and empirical studies are focused on very disaggregated (aggregated) sectoral demographic events. Preliminary spatial econometric results obtained for Belgian retailing industries confirmed the relevance of an (inter)sectoral and spatial setting for research in the interrelationship between firm births and deaths. Estimates relate to 16 retailing industries and their aggregate. However, this previous research encounters various limitations. So, from a theoretical point of view, it appears that arguments already exposed could be more explicit, as we referred to general analytical framework such as Hicks & Allen notion of complementary goods or spatial oligopolistic models that were only very briefly discussed. From an empirical point of view, data were exploited through the estimations of an econometric model which specification may reveal heavy without meaning important gains in terms of econometric accuracy or explanatory efficiency. The aims of this new paper are mainly to respond to these limitations and to give a more emphatic treatment of cross-sectoral effects. Concerning this last and more specific purpose, we test different sectoral matchings (or aggregations) and interpret the new econometric results that are obtained through this more flexible and a priori less defined statistical treatment. References DEJARDIN, M. (2001), "Firm demography in a sectoral and spatial setting", paper presented at the Third Congress on Proximity 'New Growth and Territories', Paris, December 13-14. JOHNSON, P. & S. PARKER (1994), "The interrelationships between births and deaths", Small Business Economics, 6, 283-290. JOHNSON, P. & S. PARKER (1996), "Spatial variations in the determinants and effects of firm births and deaths", Regional Studies, 30, 7, 679-688. HICKS, J. & R. ALLEN (1934, "A reconsideration of the theory of value, parts I and II", Economica, N.S., February, pp. 52-76 and May, pp. 196-219

Selecting the W Matrix. Parametric vs Nonparametric Approaches

In spatial econometrics, it is customary to specify a weighting matrix, the so-called W matrix, just choosing one matrix from the different types of matrices a user is considering (Anselin, 2002). In general, this selection is made a priori, depending on the user’s judgment. This decision is extremely important because if matrix W is miss-specified in some way, parameter estimates are likely to be biased and they will be inconsistent in models that contain some spatial lag. Also, for models without spatial lags but where the random terms are spatially autocorrelated, the obtaining of robust standard estimates of the errors will be incorrect if W is miss-specified. Goodness-of-fit tests may be used to chose between alternative specifications of W. Although, in practice, most users impose a certain W matrix without testing for the restrictions that the selected spatial operator implies. In this paper, we aim to establish a nonparametric procedure where the chosen by objective criteria. Our proposal is directly related with the Theory of Information. Specifically, the selection criterion that we propose is based on objective information existing in the data, which does not depend on the investigator’s subjectivity: it is a measure of conditional entropy. We compare the performance of our criteria against some other alternative like the J test of Davidson and McKinnon or a likelihood ratio obtained in a maximum likelihood framework.

On Diffusion of Ideas in the Academic World: the Case of Spatial Econometrics

Spatial econometrics is a fast-growing field in the series of quantitative disciplines, auxiliaries of economics and related social sciences. Space, friction, interdependence, spatiotemporal components, externalities and many other aspects interact and should be treated adequately in this field. The publication of the Paelinck and Klaassen book in the late 1970s generated virtually the field spatial econometrics This article studies the diffusion of spatial econometrics, through experienced history on the one hand, on the other through bibliometric methods. Although this field was an “Invisible College” up to 2006 (absence of any organization in form of association, conference, journal, etc.), the databases depict a fast diffusion in the past and strong prospects for the future.

Climate change promotes hybridisation between deeply divergent species

Rare hybridisations between deeply divergent animal species have been reported for decades in a wide range of taxa, but have often remained unexplained, mainly considered chance events and reported as anecdotal. Here, we combine field observations with long-term data concerning natural hybridisations, climate, land-use, and field-validated species distribution models for two deeply divergent and naturally sympatric toad species in Europe (Bufo bufo and Bufotes viridis species groups). We show that climate warming and seasonal extreme temperatures are conspiring to set the scene for these maladaptive hybridisations, by differentially affecting life-history traits of both species. Our results identify and provide evidence of an ultimate cause for such events, and reveal that the potential influence of climate change on interspecific hybridisations goes far beyond closely related species. Furthermore, climate projections suggest that the chances for these events will steadily increase in the near future

Non-isometric growth and problems of species delimitation in the genus <i>Oliva</i>

The shape of the shell of some Oliva species undergoes abrupt changes dunng growth. If undetected, this often overlooked phenomenon can cause serious errors in the delimitation of morphospecies. Examples of non-isometnc growth are reported and discussed

Selecting the W Matrix. Parametric vs Nonparametric Approaches

In spatial econometrics, it is customary to specify a weighting matrix, the so-called W matrix, just choosing one matrix from the different types of matrices a user is considering (Anselin, 2002). In general, this selection is made a priori, depending on the user's judgment. This decision is extremely important because if matrix W is miss-specified in some way, parameter estimates are likely to be biased and they will be inconsistent in models that contain some spatial lag. Also, for models without spatial lags but where the random terms are spatially autocorrelated, the obtaining of robust standard estimates of the errors will be incorrect if W is miss-specified. Goodness-of-fit tests may be used to chose between alternative specifications of W. Although, in practice, most users impose a certain W matrix without testing for the restrictions that the selected spatial operator implies. In this paper, we aim to establish a nonparametric procedure where the chosen by objective criteria. Our proposal is directly related with the Theory of Information. Specifically, the selection criterion that we propose is based on objective information existing in the data, which does not depend on the investigator's subjectivity: it is a measure of conditional entropy. We compare the performance of our criteria against some other alternative like the J test of Davidson and McKinnon or a likelihood ratio obtained in a maximum likelihood framework

The Effect of Sigmodon Hispidus on Spatial and Temporal Activity of Microtus Ochrogaster: Evidence for Competition

Spatial and temporal activities of cotton rats, Sigmodon hispidus, and prairie voles, Microtus ochrogaster, in an old-field habitat in northeast Kansas, USA were studied for 39 mo. During a major portion of the S. hispidus reproductive season the species were spatially segregated but co-occurred the rest of the year. Following a local extinction of cotton rats, prairie voles established a resident population in habitats formerly occupied by cotton rats that was greater than or equal to the vole population in areas which had never been occupied by cotton rats. Comparison of vole population size before and after the loss of cotton rats indicated that cotton rats produced a negative effect on vole population size during the period of spatial segregation but not during the period of spatial co-occurrence. Comparison of vole activity patterns indicated that, with the loss of cotton rats, voles shifted their activity during times when the species had co-occurred but not during periods when they were spatially segregated. Studies of behavioral interactions in a large (4 m x 4 m) arena with varying densities of vertical wires indicated that during single species tests voles and cotton rats preferred the densest areas. Their diel activity patterns were broadly overlapping. In the presence of nonreproductive cotton rats, voles continued to use the same areas as during the control tests but shifted their temporal activity reducing overlap with cotton rats. Interspecific encounters resujted in voles avoiding cotton rats even in the absence of overt aggression. In the presence of reproductive cotton rats, voles shifted their arena usage toward areas least used by cotton rats. Total nocturnal activity by voles was the same as during the control tests but was restricted to hours when cotton rats were least active. Reproductive cotton rats showed higher levels of interspecific aggression than did nonreproductive cotton rats. Voles in the presence of reproductive cotton rats showed increased frequency of serious wounds and deaths, and decreased mass when compared to voles in the presence of nonreproductive cotton rats. We conclude that cotton rats produce a negative effect on prairie vole populations but that the interaction is restricted to the cotton rats' reproductive season. Coexistence of the species appears to rely on the seasonality of the interaction, habitat heterogeneity, and the wider habitat tolerance of prairie voles

Genetic variation during range expansion: effects of habitat novelty and hybridization

How species' ranges evolve remains an enduring problem in ecology and evolutionary biology. Species' range limits are potentially set by the inability of peripheral populations to adapt to range-edge habitat. Indeed, peripheral populations are often assumed to have reduced genetic diversity and population sizes, which limit evolvability. However, support for this assumption is mixed, possibly because the genetic effects of range expansion depend on two factors: the extent that habitat into which expansion occurs is novel and sources of gene flow. Here, we used spadefoot toads, Spea bombifrons, to contrast the population genetic effects of expansion into novel versus non-novel habitat. We further evaluated gene flow from conspecifics and from heterospecifics via hybridization with a resident species. We found that range expansion into novel habitat, relative to non-novel habitat, resulted in higher genetic differentiation, lower conspecific gene flow and bottlenecks. Moreover, we found that hybridizing with a resident species introduced genetic diversity in the novel habitat. Our results suggest the evolution of species' ranges can depend on the extent of differences in habitat between ancestral and newly occupied ranges. Furthermore, our results highlight the potential for hybridization with a resident species to enhance genetic diversity during expansions into novel habitat