(11 fhe extent to which the lever of production by v.r~riat:les in fa•;.U>rs of production and capital. systell'~ o1T :i.t.:ti"'!·'-~r'cs JH':::>c.>Jpposes u·•e dV.iilabdlty of of data• namely: is affected A reliable two t.'fpE's :aJ f4.:J!i ic -r:qrir;u1ttJ!T',lf data-. i.e. reldt:ing to stable fac­ t:.mr-s., ttot subJect to 'ier:Jsonal variations.- and derived f'!·O\W aqri­ cultu•·at censuses car,.ied out at *ong intervals-. e.g. once every five or ten yearsi and {b) Current agricultural d~ta~ i.e. which varies fro~ one season to, anothe,. and, even, wittun the same season... Such data is obtained through studies conducted either per"iodicalfy, in accordance with a fixed schedule (ye.uly., quar"terly. atonthly Of" t.!Yen weekly., if necessar"y)-. of" at irYegular intervals, as the need <uises, or yet once onfJ• in order to collect data needed for a specific purpose in connection with oper-ations that ~night never be repeated. -2 - II-METHODS USED TO COlleCT 04TA ON AGRltOlTURE The successive agricultural censuses carried out in various Governorates since 1978 constitute the ffrst attempt ever to coflect basic statistical data on the agricultural sector through field studies on villages and fa..-me rs. Contrary to nor­ Mat practice. howeYer-, these were not all conducted in the same agricu1tural year, but their findings temporarily meet the des­ parat.e need for data and can be utilized penaing the completion of a general agr-icuttural census. FOf" convenience the censuses wer-e carried out using t~e sampling methodw successively in the Governorates of Ohamar. Al-Hodei<lah., flajja .. Al-Mahweetw Taiz. lbb, sa•ada, Af-Seida, Sana•a. AI 3ow~ and Ma•reb. The sampling method adopted is pr-esented below, together with the method used to pr-epare the fra~e and select primary units and holdings. The agricurturar censuses were carri'ed out on stratified random samples in two stages. Accordingly. two frames had to be p.-eparedw before the sample of holdi.ngs could be selected• name­ fy 
**Analysis**
The text appears to be discussing the collection and analysis of data related to agriculture, specifically the agricultural sector in Yemen. The text mentions the importance of reliable data, the use of sampling methods, and the collection of data through field studies and censuses. The context suggests that the data is being collected for the purpose of understanding and developing the agricultural sector, which is a key aspect of economic development.

**Category**
Agriculture, forestry and fishing