土地利用规划中人口预测模型的比较研究

研究目的:研究土地利用规划中几种常用人口预测模型的特点和适用条件,为土地利用总体规划编制工作服务.研究方法:统计分析法和对比分析法.研究结果:利用人口历史统计数据建立预测模型,分时段进行预测,并与实际观察值比较,得出预测误差的大小,通过预测误差大小的分析比较,总结了各种预测模型的特性与适用条件.研究结论:一元线性回归法适用于数据直线趋势较明显的预测;历史数据较少时,可用指数平滑和移动平均数法;数据情况复杂时可采用GM(1,1)模型法;自然增长率等资料准确可靠时可采用人口自然增长法或马尔萨斯法;宋健模型法用于短期预测的精度较高;土地规划中人口预测应多种预测方法综合运用.     

FORECASTING SAWNTIMBER CONSUMPTION: THE APPLICATION OF AN END-USE MODEL*

A multi-equation end-use model is used to analyse the consumption of sawn-timber in Australia. The forecasting ability of the model is evaluated. Simulations of the model are reported and implications for policy are discussed.     

Short-run Dynamics of Machinery Demand in Canadian Agriculture

Based on the hypothesis of intertemporal cost minimization, this paper develops an error correction model to explain short-run dynamics of machinery demand in aggregate Canadian agricultural production. The estimated model is subjected to a rigorous sequence of hypothesis tests to check for its statistical validity. In addition, various versions of the model that are nested within the most general model are also tested. Structural parameters of the intertemporal cost minimization problem are recovered from the parameter estimates.     

基于BP网络的水利建设项目社会评价

选取水利建设项目社会评价中的12个评价指标作为学习样本,建立3层BP神经网络模型,用8组数据对所建网络模型进行训练,选取两个水利建设项目数据来检验已经训练好的网络模型,最后将此模型应用到湖南省江垭水利枢纽工程社会评价中,与模糊层次分析法的评价结果相比较,表明BP神经网络用于水利工程社会评价的优越性。     

OPTIMAL BUFFER STOCK POLICIES FOR WHEAT AT THE WORLD LEVEL

Alternative wheat storage policies which maximise the expected present value of returns for consumers, producers, a monopoly storage agency and society as a whole are derived using a dynamic programming model. Results are compared with those from an earlier simulation model, and are found to justify higher investment in storage capacity compared with that suggested by the simulation model. The model is extended to derive optimal storage policies if production follows a stochastic cobweb process.     

A generalized Armington trade model: Respecification

Even if the original version of the Armington model is simple and plausible in estimation, the single CES and homotheticity assumptions are too restrictive for practical application and give biased price elasticities. This paper develops a generalized Armington model, which relaxes the single CES and homotheticity restrictions, and includes the Armington model as a special case. The Armington and generalized Armington trade models are applied to the Japanese meat import demand to demonstrate their performance. The empirical results rejected the two assumptions imposed on the Armington model. The generalized Armington model provides an alternative to the restrictive but indispensable Armington model.     

Measuring market integration in the presence of transaction costs–a threshold vector error correction approach

Applied econometric analyses of market integration based on price data alone have been criticised because they neglect the role of transaction costs. To meet this objection, threshold vector error correction models are used. Threshold models can account for the effects of transaction costs in price transmission without directly relying upon information about these costs, which are often unavailable. It is argued that threshold models that are based on two thresholds provide results that are economically more intuitive than those obtained from one-threshold models. However, to this point no adequate econometric test is available for threshold significance in a two-threshold model; such tests are only available for the one-threshold model. In this paper a restricted two-threshold model is developed in which the significance of the thresholds can be tested. This model is therefore amenable to economic interpretation and statistical inference. The model is used to estimate market integration in the European pig market.     

A spatial high-resolution model of the dynamics of agricultural land use

An area model is presented for agricultural land use, based on a generalized linear mixed model. This model is spatially explicit and dynamic and, although it uses aggregated data, allows for heterogeneity of behavior among individual farmers. The parameters of the fixed component of the model are obtained using an estimation equations approach, and the structure of spatiotemporal correlation is assessed using empirical semivariograms. The model is illustrated using as an example the dynamics of agricultural land use in the Lower Guadalquivir area in Spain. A simulation study indicates that the model gives poor results if the heterogeneity of individual behavior and spatiotemporal autocorrelation are ignored.     

PRICE-LINKED FARM AND SPATIAL EQUILIBRIUM MODELS

The integration of detailed farm supply models with the basic spatial equilibrium model, is outlined. The direct linking of farm linear programming models with the spatial equilibrium model is achieved so that both prices and quantities are endogenous. Both the farm model and the spatial equilibrium model must be specified in primal-dual form to make the linkages. Limited details of the use of such a model in a study of a segment of the grain handling system in New South Wales are presented along with conclusions relating to the pricing of grain handling services.     

A NOTE ON DISTRIBUTED LAG MODELS OF MAIZE AND WHEAT PRODUCTION RESPONSE: THE KENYAN CASE*

In this note the supply responses in maize and wheat production are estimated from distributed lag models. The Nerlove model and the Fisher distributed lag model fit Kenyan data but more complicated models, like the polynomial lag model, do not. The calculated price elasticities suggest that Kenyan large-scale farmers are highly responsive to price changes. Some policy implications are drawn from the analysis.     

ESTIMATION OF A PRODUCTION FRONTIER MODEL: WITH APPLICATION TO THE PASTORAL ZONE OF EASTERN AUSTRALIA

This paper considers a statistical model for a production frontier that is consistent with the traditional (nonstochastic) definition of a production function given in microeconomic theory. Limiting cases of the model are the familiar average production function and an envelope production function. Maximum-likelihood estimators for the parameters of the model are defined. The three related models are applied in the estimation of a production frontier for the Pastoral Zone of Eastern Australia with use of data from the Australian Grazing Industry Survey.     

ALTERNATIVE BREEDING INVENTORY SPECIFICATIONS IN A LIVESTOCK MARKET MODEL

The procedures adopted for incorporating breeding decisions in a livestock market model have implications for the simulation of the model. Specifically, there is a need to consider the nature of the biological lags between livestock breeding decisions and outputs, and how these are incorporated in the breeding inventory used in such a model. In this paper, five alternative breeding inventory specifications are used in a structural econometric model of the Australian prime lamb market. The predictions of lamb slaughterings and of price responses of lamb producers are affected by the specification of the lamb breeding inventory used. The extent to which the modelling results approximated reality was substantially improved when disaggregated and seasonally allocated data were used to estimate lamb breeding inventories.     

The demand for alcoholic beverages in Spain

The objective of this study is to analyze the main determinants of alcoholic beverages consumption at home. Data comes from the latest Spanish Household National Survey, which provides information on expenditure and quantities of different food products by household. Because households are interviewed only 1 week, a large number of zeros have been recorded. Among the existing censured demand models (the double hurdle (DH) model; the purchase‐infrequency model; and the Tobit purchase‐infrequency model, among others) and after carrying out model selection tests, the DH model has been finally estimated. All expenditure elasticities are positive, corresponding the highest value to spirits. Own price elasticities are negative and also in this case the spirits exhibit the highest value. Socio‐economic variables also play an important role in explaining consumer purchase and consumption decisions.     

Dynamic factor demand equations in U.S. and Canadian agriculture

This research provides one of the first empirical estimates of a data-based dynamic factor demand model for American and Canadian agriculture. Models such as these deserve more widespread use in the empirical analysis of agriculture. These models have the advantage that they do not impose inappropriate dynamics on the data. Rather they permit the data to select the appropriate dynamics. We use a model originally developed by Anderson and Blundell. This model is a general first-order dynamic model which contains as testable hypothesis several simpler models. This model permits us to estimate the long-run agricultural production structure as a subset of the dynamic parameter estimates. We will test this long-run structure for symmetry, homotheticity and neutral technical change. The estimated models may be used to test for three alternative dynamic structures. In the limit, dynamics may not be needed and we can test for the static long-run equilibrium model. Two intermediate cases are the autoregressive and the partial adjustment models which are simpler than the general model but still include dynamics. Our results suggest that the long-run equilibrium model is unsatisfactory in both countries. A dynamic model is needed. In both countries, the two more restricted dynamic models are rejected. The general dynamic model is required. In Canada, the long-run equilibrium structure is homothetic with neutral technical change. In the United States, homotheticity is also accepted but neutral technical change is rejected.     

农民对林业合作模式倾向的实证研究——基于南方五省的调研结果

基于对南方5省的实证调研,从农户认知的角度对合作模式分类,用多元Logistic回归模型分析了林农对合作模式的倾向性和影响因素,并找出了影响较大的变量取值范围。研究发现:农户对合作模式的倾向依次是:加入合作组织、联户经营、公司+农户和其他合作模式。影响显著的农户特征变量有:省份、年龄、文化程度和劳动力数量,农户需求变量有:技术服务、资金、市场信息和采伐指标的支持。在此基础上,分别对不同合作模式的选择与引导提出了建议。     

Simulating the Impacts of Contract Supplies in a Spot Market–Contract Market Equilibrium Setting

This article embeds a principal–agent model within a market equilibrium model of contract and cash markets to analyze the impact of contracting on the spot market for hogs. The equilibrium model incorporates both quality differentiation in the contract market and an endogenously determined cash market price. For three types of contracting scenarios, market equilibrium conditions are derived, and results are presented for a numerical example. Contrary to some empirical results, our model shows that the increased supply of hogs under typical formula-price contracts can increase or decrease the cash market price, depending on the relative size of overall contract supplies.     

The income earned by women: impacts on welfare outcomes

This paper provides an updated review of the evidence on income pooling across household members. Income pooling is one of the main predictions of the unitary model of the household. New studies come to much the same conclusion as do past studies: income pooling and the unitary model are rejected. The paper then looks beyond the mere rejection of the unitary model and explores some of the issues that arise. First, what is the progress in testing the restrictions imposed by non-unitary models of the household? Second, what are the implications of rejection of the unitary model for policy and program design? Finally, what are some of the challenges faced by programs and policies that internalize the rejection of income pooling in terms of impact evaluation?     

Area Allocation Under Price Uncertainty on Dutch Arable Farms

This paper uses a Mean-Variance utility function to build a dual model that simultaneously determines area allocation and production/input levels under output price uncertainty. Regularity conditions of the indirect utility function (convexity) and producers risk preferences are tested. The framework is applied to a rotating sample of Dutch arable farms. Dutch arable farmers are found to be risk averse, with the size of the risk premium given by 3 per cent of annual profit. A bootstrap resampling method shows that curvature conditions are rejected. Price elasticities are compared for an unrestricted model and for a model with curvature conditions being imposed.     

A Multivariate Sample-Selection Model: Estimating Cigarette and Alcohol Demands with Zero Observations

Heckman's sample-selection model is generalized to the multivariate case and used to estimate demands for cigarettes, beer, and wine by individuals in the United States. The specification allows correlations between the error terms of multiple selection and level equations, and nests the popular bivariate sample-selection model and two-part model. Empirical results suggest that the proposed model performs better than the restricted specifications. Differentiated effects of variables on probabilities and levels of consumption also suggest rejection of the Tobit system. Gender differences are present, and demographic variables are more important than income in determining consumption of cigarettes, beer, and wine.     

水资源评价方法及其应用

水资源具有多种用途。其使用价值的评估对水资源的规划与利用至为重要;探讨不同水资源用途依其经济属性的评价方法及其应用范围和限制;所讨论的评价方法包括：旅行成本法、特征价格法、假设条件评估法、以及生产函数法等５种。