Policymakers, farmers, managers of agriculture and others look to agricultural economists for accurate estimates of the costs and returns of individual agricultural commodities. But there is great diversity and disagreement among practitioners about the best method for such analysis. The contributors to this volume explore how different uses of estimates determine different methods of estimation, as well as evaluating what the preferred methods are for similar uses.

In this book we assemble a range of evidence from a range of sources with a view to developing an improved understanding of recent trends in agricultural productivity around the world. The fundamental purpose is to better understand the nature of the long-term growth in the supply of food and its principal determinants. We pursue this purpose from two perspectives. One is from a general interest in the world food situation in the long run. The other is from an interest in the implications of U.S. and global productivity patterns for U.S. agriculture.

vate, operate, or manage a farm for profit, either as owner or tenant. A farm includes livestock, dairy, poultry, fish, fruit, and truck farms. It also includes plantations, ranches, ranges, and orchards and groves. This publication explains how the federal tax laws apply to farming. Use this publication as a guide to figure your taxes and complete your farm tax return. If you need more information on a subject, get the specific IRS tax publication covering that subject. We refer to many of these free publications throughout this publication. See chapter 16 for information on ordering these publications. The explanations and examples in this publication reflect the Internal Revenue Service's interpretation of tax laws enacted by Congress, Treasury regulations, and court decisions. However, the information given does not cover every situation and is not intended to replace the law or change its meaning. This publication covers subjects on which a court may have rendered a decision more favorable to taxpayers than the interpretation by the IRS. Until these differing interpretations are resolved by higher court decisions, or in some other way, this publication will continue to present the interpretation by the IRS.

Using data on 34 countries in Africa south of the Sahara (SSA) from 1980 to 2012, this paper assesses the returns to public spending in the agricultural sector, considering expenditures on agriculture as a whole versus expenditures on agricultural research. First, an aggregate production function is estimated using a fixed-effects, instrumental variables estimator to address potential endogeneity of agricultural expenditure and to obtain elasticities of land productivity with respect to total agricultural expenditure and agricultural research expenditure. Different model specifications are used to test the sensitivity of the results to different assumptions. The estimated elasticities are then used to estimate the rate of return to expenditure in different countries and groups of countries. The elasticity of land productivity with respect to total agricultural expenditure per hectare is estimated at 0.04, and elasticity with respect to agricultural research expenditure per hectare is estimated to be higher at 0.09. The aggregate returns to total agricultural expenditure and agricultural research expenditure in SSA are estimated at 11 percent and 93 percent, respectively. Comparative analysis of the estimates with those of previous studies, as well as across different countries and different groups of countries, is undertaken. Then implications are discussed for maintaining the high returns to agricultural research expenditure and for further studies on the low return to total agricultural expenditure, including more disaggregated analysis of expenditure on other functions besides research to better inform prioritization of agricultural expenditure.