In order to establish uniform criteria with a standardized model for objective review and inter-pretation of the results, this paper evaluates the strengths and weaknesses of current methodologies for FTA impact analysis and addresses the problems in interpretation of the estimated values from previous studies. This paper reviews previous works, assessing the impacts of FTA from the perspective of the models and key variables used in the analytical model, criteria and periods for the damage assessment, and the difference between net damage cost and cumulative damage cost. A number of inconsistences are found in previous studies to explain the importance of promoting FTA. Although the research objective may vary for different countries, consistent application was not found in prior studies for the major variables used in their economic models, including measurement standards, effectiveness factors, and the ripple effect estimation period. The inconsistent results from these studies fail to explain as well as persuade the national assembly and stakeholders of the consequences of FTA on the agricultural sector. The frequent criticisms from non-agricultural sectors are that the negative effect of FTA on the agricultural sector is overestimated, whereas from the agricultural sector, the effect is underestimated.