RESOURCE USE IN SYSTEMS OF INTENSIVE ANIMAL PRODUCTION

The purpose of this paper is to describe several alternative mixes of resources used in animal production, explain why they came about, and question their appropriateness. My main thesis is that capital-intensive systems, although not inherently good or bad, have social and economic consequences for a country that may be either very good or very bad.Livestock Production/Industries,

Confidence Regions for Robust Regression

This paper describes the results of a Monte Carlo study of certain aspects of robust regression confidence region estimation for linear models with one, five, and seven parameters. One-step sine estimators (c = l.42) were used with design matrices consisting of short-tailed, Gaussian, and long-tailed columns. The samples were generated from a variety of contaminated Gaussian distributions. A number of proposals for covariance matrices were tried, including forms derived from asymptotic considerations and from weighted-least squares with data dependent weights. Comparisons with: the Monte Carlo "truth" were made using generalized eigenvalues. In order to measure efficiency and compute approximate t-values, linear combinations of parameters corresponding to the largest eigenvalues of the "truth" were examined. For design matrices with columns of modest kurtosis, the covariance estimators all give reasonable results and, after adjusting for asymptotic bias, some useful approximate t-values can be obtained. This implies that the standard weighted least-squares output using data-dependent weights need only be modified slightly to give useful robust confidence intervals. When design matrix kurtosis is high and severe contamination is present in the data, these simple approximations are not adequate.

SOME SPECULATIONS ON THE LONG RUN FUTURE OF RICE IN THAILAND

Crop Production/Industries,

TECHNOLOGY AND THE AGRICULTURAL OUTPUT MIX

The purpose of this paper is to show how the allocation of research resources among commodities and the effects of such allocations on the output mix depend upon (a) the initial production conditions, (b) the nature of the research production functions, and (c) the nature of the demand relations for the commodity outputs. The basic model used is a two-factor, two-product model in which certain types of technical change are introduced.Farm Management,

ENVIRONMENTAL CONSTRAINTS, COMMODITY MIX, AND RESEARCH RESOURCE ALLOCATION

The purpose of this paper is to show how the allocation of research resources among commodities and the effects of such allocations on the output mix depend upon (a) the initial production conditions, (b) the nature of the research production functions, (c) the nature of the demand relations for the commodity outputs, (d) relative factor endowments, and (e) the existence of different types of environmental constraints. The basic model used is a two-factor, two-product model in which certain types of technical change are introduced.Research and Development/Tech Change/Emerging Technologies,

RICE IN THAILAND

Crop Production/Industries,

Linear Regression Diagnostics

This paper attempts to provide the user of linear multiple regression with a battery of diagnostic tools to determine which, if any, data points have high leverage or influence on the estimation process and how these possibly discrepant data points differ from the patterns set by the majority of the data. The point of view taken is that when diagnostics indicate the presence of anomolous data, the choice is open as to whether these data are in fact unusual and helpful, or possibly harmful and thus in need of modifications or deletion. The methodology developed depends on differences, derivatives, and decompositions of basic regression statistics. There is also a discussion of how these techniques can be used with robust and ridge estimators. An example is given showing the use of diagnostic methods in the estimation of a cross-country savings rate model.

BACKGROUND TO THE INTRODUCTION OF HIGH YIELDING VARIETIES OF RICE IN THAILAND

This paper describes Thailand's experience to date with new technology in rice, namely new high yielding varieties with associated inputs, which forms one part of the "green revolution." First, the historical background in exports, production, and domestic marketing and pricing is presented. Next the significant developments in rice research in Thailand are described, followed by a brief outline of the adoption of new varieties. In the final section, some implications are drawn for future developments, based on the experience gained until now.Crop Production/Industries,

The Variances of Regression Coefficient Estimates Using Aggregate Data

This paper considers the effect of aggregation on the variance of parameter estimates for a linear regression model with random coefficients and an additive error term. Aggregate and microvariances are compared and measures of relative efficiency are introduced. Necessary conditions for efficient aggregation procedures are obtained from the Theil aggregation weights and from measures of synchronization related to the work of Grunfeld and Griliches.