MULTIDIMENSIONAL OUTPUT INDICES

This abstract describes alternative output aggregates that provide both cross-sectional and temporal comparisons appropriate for the analysis of panel data sets. Several of these multidimensional output indices are constructed using detailed data on agricultural production to illustrate the effects of fixing price weights over time, employing sample average price weights, and choosing between alternative approximations of Divisia indices.Research Methods/ Statistical Methods,

PATTERNS OF AGRICULTURAL DEVELOPMENT IN THE UNITED STATES

International Development,

The Influence of Predator-Prey Population Dynamics on the Long-term Evolution of Food Web Structure

We develop a set of equations to describe the population dynamics of many interacting species in food webs. Predator-prey interactions are non-linear, and are based on ratio-dependent functional responses. The equations account for competition for resources between members of the same species, and between members of different species. Predators divide their total hunting/foraging effort between the available prey species according to an evolutionarily stable strategy (ESS). The ESS foraging behaviour does not correspond to the predictions of optimal foraging theory. We use the population dynamics equations in simulations of the Webworld model of evolving ecosystems. New species are added to an existing food web due to speciation events, whilst species become extinct due to coevolution and competition. We study the dynamics of species-diversity in Webworld on a macro-evolutionary timescale. Coevolutionary interactions are strong enough to cause continuous overturn of species, in contrast to our previous Webworld simulations with simpler population dynamics. Although there are significant fluctuations in species diversity because of speciation and extinction, very large scale extinction avalanches appear to be absent from the dynamics, and we find no evidence for self-organised criticality.Comment: 40 pages, preprint forma

Medical Malpractice Litigation Under National Health Insurance: Essential or Expendable?

Identification of time-continuous models from sampled data is a long standing topic of discussion, and many approaches have been suggested. The Maximum Likelihood method is asymptotically and theoretically superior to other methods. However, it may suffer from numerical inaccuracies at fast sampling and it also requires reliable initial parameter values. A number of efficient and useful alternatives to the maximum-likelihood method have been developed over the years. The most important of these are State-Variable filters, combined with Instrumental Variable methods, including the simplified refined IV method. In this contribution we perform unpretentious numerical experiments to comment on these methods, and their mutual benefits.CADIC

INTERNATIONAL AGRICULTURAL PRODUCTIVITY PATTERNS

In this paper we present measures of land and labor productivity for a group of 98 developed and developing countries using an entirely new data set with annual observations spanning the past three decades. The substantial cross-country and intertemporal variation in productivity in our sample is linked to both natural and economic factors. We extend previous work by dealing with multiple sources of measurement error in conventional agricultural inputs when accounting for observed differences in productivity. In addition to the mix of conventional inputs in agriculture, we find that indicators of quality change in these inputs and the amount of publicly provided infrastructure are significant in explaining cross-sectional differences in productivity patterns.Productivity Analysis,

Dependence of Galaxy Shape on Environment in the Sloan Digital Sky Survey

Using a sample of galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 4, we study the trends relating surface brightness profile type and apparent axis ratio to the local galaxy environment. We use the SDSS parameter `fracDeV' to quantify the profile type. We find that galaxies with M_r > -18 are mostly described by exponential profiles in all environments. Galaxies with -21 < M_r < -18 mainly have exponential profiles in low density environments and de Vaucouleurs profiles in high density environments. The most luminous galaxies, with M_r < -21, are mostly described by de Vaucouleurs profiles in all environments. For galaxies with M_r < -19, the fraction of de Vaucouleurs galaxies is a monotonically increasing function of local density, while the fraction of exponential galaxies is monotonically decreasing. For a fixed surface brightness profile type, apparent axis ratio is frequently correlated with environment. As the local density of galaxies increases, we find that for -20 < M_r < -18, galaxies of all profile types become slightly rounder, on average; for -22 < M_r < -20, galaxies with exponential profiles tend to become flatter, while galaxies with de Vaucouleurs profiles become rounder; for M_r < -22, galaxies with exponential profiles become flatter, while the de Vaucouleurs galaxies become rounder in their inner regions, yet exhibit no change in their outer regions. We comment on how the observed trends relate to the merger history of galaxies.Comment: 23 pages, 7 figures, accepted by Ap

U.S. AGRICULTURAL RESEARCH DEFLATORS: 1890-1985

Using newly developed time series on U.S. public sector agricultural research expenditures, two new deflators for agricultural research are constructed. These deflators differ from others currently used in the literature in that factor level price indices are weighted with time varying weights which capture the shifting factor mix of research spending by the state agricultural experiment stations (SAES). The substantial differences in measuring real resource allocation to agricultural research using these deflators and alternatives found in the literature, including that used by the National Science Foundation to report official R&D statistics, are demonstrated. In addition, the factor level expenditure series are used to contrast measurement of resource allocation in agricultural research from 1890 to the present using real research service flows as opposed to real research expenditures.Research and Development/Tech Change/Emerging Technologies,

The Internal Proper Motions Of Stars In The Open Cluster M35

Relative proper motions, based on 108 orbits of Hubble Space Telescope Fine Guidance Sensor data extending from 1992 to 2006, are reported for 74 stars in the open cluster M35 (NGC 2168). A subset of 22 of these objects are then used to compute the cluster's internal proper motion dispersions in both right ascension and declination. We find that these dispersions are equal to within their measurement errors. The average one-dimensional dispersion is 0.018 +/- 0.002 arcsec century(-1). When combined with the M35 radial velocity dispersion of 0.65 +/- 0.10 km s(-1) found by Geller et al., this produces a cluster distance of 762 +/- 145 pc. Using isochrone fits to the cluster main sequence, this distance suggests that M35 has an age of about 133 Myr. Although this age is consistent with that typically found for M35, the formal error in the dynamical distance of +/- 19% can accommodate ages between 65 Myr and 201 Myr.McDonald Observator