S.M.I.: minimum installation surface area setting per small region the surface areas below which installations must no longer be encouraged. This was defined initially as the surface area for a multi-crop and stock farm on which a young household could earn a minimum income.

In the field of social protection for farmers it is used as a basis for defining the threshold for being subject to the agricultural social regime > a minimum of ½ S.M.I. must be farmed in order to be affiliated to the M.S.A., and benefit from the status of farmer.

The S.M.I. is set by ministerial order for each county, within the master plan for agricultural structures prepared and set by the Prefect, after advice from the General Council, the Chamber of Agriculture and the County Commission for Agricultural Direction. It is revised periodically.

It is set for each county by zone (e.g. plain zone or so-called underprivileged zone) and is weighted according to the type of crops (S.M.I. different depending on the crop: pasture, land suitable for mechanical farming, vines, trees, etc.). Non-land production S.M.I. are national (the same in every county).
 
Example of S.M.I
In the county of Vienne, the S.M.I is 25 ha for the plain zone and 34 ha for the “underprivileged” zone.