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and the prices of imported agricultural inputs are instruments at the discretion of the Ministry of National Economy and the Ministry of Finance. Consequently, policy analysis based on these instruments tended to engender little interest on the part of the Ministry of Agriculture officials. On the other hand, instruments that were later discovered to be at the discretion of the ministry, such as storage and transportation services, do not presently appear in the model. This obviously suggests directions for future modifications of the Tunisian model.
The desirable degree of instrument "resolution" (i.e., the time, place, form) and control, and the "real" objectives are often even difficult for policy-decision making authorities to articulate. To comprehend fully the array of instruments and structural characteristics at the disposal of the policy makers implies a need to understand the policy-making process, the capacity and effectiveness of the policy implementing machinery and to be aware of the human frailities and general behavior of these institutions. We suggest that this is the importance of the dialogue between model builder and planner as discussed by Kornai
(9) and the need to consider the institutional constraints as advanced by Sherbini (7).
It also appears to us that plans designed for making ASA techniques an integral part of the policy-decision making and program implementing framework of a ministry delegated with this responsibility, must recognize and take into consideration that traditional channels for information flow between policy-decision making authorities and program implementing agencies have developed over a period of time. Consequently, these