Agricultural economics is a field of applied economics. Its scope and its relationship to other social and natural science disciplines has changed over time in response to (a) the social, economic and technical changes impinging on the agricultural sector and (b) progress in economic theory and in other related social and natural science disciplines. The substance of agricultural economics in the United States at the present time can best be understood by reviewing the historical origins of the field and its recent evolution in relation to developments in economic theory, statistics and econometrics.