The aim of paper is to verify validity of some hypotheses which explain income disparity of agriculture under conditions of the current European agricultural model, and further to suggest a possible approach to categorization of this phenomenon. It is not dealt with all hypotheses which were expressed in connection with the income disparity, but also with those oriented to costs. Demand-oriented hypotheses will be a subject of further research. On base of the reached grade of knowledge, the present validity of hypotheses explaining farmers ́ income disparity by the help of specialities of agricultural production, alternative costs, and introduction of technical progress (Theory of treadmill) is analyzed.