modelization of the agric~1tural sector involves a knowledge of the production technologies and of people•s economic beh~viour. In the two examples given above on project anctlysis and sectoral plannlnq models~ the tewel of disaggregation of the data ~as very small, the modets relyinq on farm-survey da~a differentiating between the nature of ownership. etc. One can rou-ghly di st. i ngo'i sh three types of information to be col­ lected: (1) .farm management oat a: production techno I agies, input and out­ put farmgate prices. produ:ction costs according to the different. tech­ nologies. land ana working capital ownership. labour requirements; 12 -lJ - (2) Farl'lers• b~hav,our; fa.-m~rs • consumptio n dlod S<~vinq patterns, attitudes towards risk. use of credit. co-op~rative me~bership; (3) Jhe demcmd ancs marketing of agricultural commo -:htaes: t"e demand for food. the d\jrv-industries• requirement s. tt1e marketing channels organization and profit margins, the wholesale and retai I prices. These data dre typically of a m~cro ·economac nature, in oppo­ sd.:i•.)n to the qu.:dit.ci't .i'le procedural ::·E:quin~·ment~ of :";tacro-economic d;:•'tcJ• .!f 'itt,lt istics about macro-aggregates are rather abundant in the pubi~cations of the statistical organizations in the ECWA countries, information at the micro-level is quite scarce. This l.act< of informd­ tion caA be eKplained by the fo11o~ing problems. f_i!.st.- 21nd IVJ~inly.. the organizational problems encounter ed in collectin g ~icro-type data. Since the disaggregation level is sma•l and some of the 'lata have a strong seasonal component• the systP.matic collection of r.:-:t~ iofcnr<dt.ion implies,. i!!!.~~ !.i!!.:!. the decentr-.il i·­ ~dtion of the statistical offices. the diversific~tion of the data ~~urces together ~ith the systematizing of the targeted sample sur­ v~ys, and the institution of permanent contacts at the Jocal !evel ,tittl t:ne org.1rd.J. ~l~.ion~ ~nvo,ved. in agric..ulturP. {adm!n!st.!'at:h ~o: n~-ope:-atives • .a~.Jr-o-inc1astt·ies .. wholesale llt.Jrkets,). ·Joviously suc:h a 