could be selected and used to represent social values and goals, applying the interpretation of the users. 3 7. The comprehsnsiveness of he statistrcal series in SSDS could pro­ vide a good point of departure in formulating a country-specific social indicators structure. In using this global system, extreme care should be given in the process of selecting statistical series to be included in a country-specific system. Those included should be significant and rele­ vant in the context of current and near future development of the coun­ try concerned. Furthermore, SSDS would also serve as a useful reference 28 Although the proposed set of indicators i<l relatively small, it includes four indicators on non-human productive resources and five experimental indicators on political values, remind­ ing a reader of the world-wide resource cruis and the political situation in the Philippines in the early l 970s. 29 Towards a System of Social and Demographic Statistics, op. cit., pp. 3 -4. 45 to the statistician involved in a social indicators project, whose primary responsibilities are to provide the empirical contents of a conceptually formulated system and to enhance the efficiency and comprehensiveness of its data collection system. Providing statistical contents 38. In order to be practically useful, a conceived system of social indicators must be expressed in numbers, either cross-sectional and/or in time series. The sources of numerical data for social indicators are, of course, censuses, surveys, and reported statistics compiled by govern­ ment and private statistical agencies. Because of this interrelationship, social indicators are often identified as social or socio-demographic statis­ tics. 39. For developed countries, the provision of statistical contents to a social indicators system poses relatively little problem owing to the abun­ dance of available data, meeting most statistical requirements. Three conceivable problems relevant to providing the statistical contents of a system of social indicators often encountered in advanced countries are 