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101.
A biologically realistic model of crop yield response to herbicide application is presented. It includes functions for weed mortality from herbicide application and yield loss due to surviving weeds. The optimal herbicide rate and two types of decision thresholds are derived theoretically and illustrated with empirical examples. Responses of the various decision criteria to changes in parameters are also examined theoretically and empirically. A multidimensional threshold for weeds based on weed density and weed-free yield is presented. The issue of farmers using other than officially recommended herbicide rates is discussed. 相似文献
102.
Why Farmers Quit: A County-Level Analysis 总被引:1,自引:0,他引:1
Stephan J. Goetz & David L. Debertin 《American journal of agricultural economics》2001,83(4):1010-1023
We identify the effects of alternative explanatory variables on the propensity of U.S. farmers to cease farming, with a particular emphasis on understanding the roles of off-farm employment and federal farm program payments. Conventional ordinary least squares analysis using all counties suggests that off-farm employment has no statistical effect on the (net) number of farmers quitting between 1987 and 1997, ceteris paribus . A more refined analysis, which separates counties losing farmers from those that gained farmers, reveals subtle and less clear-cut effects of off-farm employment (and federal program payments) on farm exits. 相似文献
103.
Changes in exporter market shares in the Kuwaiti poultry import market over the period 1971–81 are analysed by three modelling procedures. Two traditional approaches, a first-order constant transition probability Markov model and a set of market share equations, are found to be of only limited use. As an alternative, a multinominal logit model of market share behaviour is estimated. The empirical results indicate that, in addition to relative price changes, domestic policy inducements for Brazilian and European Community exports are important in determining market share changes. A comparison of the explanatory abilities of the models suggests that the multinominal logit model is as least as good as traditional modelling alternatives with respect to econometric criteria. It is concluded that the multinominal logit model offers considerable promise as a tool for market share research. 相似文献
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For firms manufacturing convenience goods there are three branding policies available, a proprietory brand policy, a retailer brand policy and a mixed brand policy. A firm's choice depends on differences in demand and promotion costs between the proprietory and retailer brand markets. This can be analysed using a simple elaboration of the standard 3rd degree price discrimination model. But if the two markets are not independent over the long-term there may be other consequences of following the optimization rules of the model. If retailers develop consumers' preference for their own shops and their own brands, the demand advantage enjoyed by manufacturers' brands may be reduced further. The more willing are manufacturers to supply retailer brands, the more retailers win undermine the demand for manufacturers' proprietory brands. 相似文献
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