35 This point was made during the course of the Expert Group Meeting by the particl-· pant from the United States. so model building; little progress has been made owing to the lack of statis­ tical contents of social indicators and of established theories relating eco-. nomic and social factors. The available series of _social statistics are not only extremely -limited, but· also lack universally applicable definitions and data. Despite data limitations, pioneering works in this area were attempted independently ·by Fredrick Harbison and others 36 ·and by · Irma Adelman and Cynthia T. Morris.37 In their studies, the authors seem to have struggled a great deal in search of appropriate quantitative · techniques for their analysis .. Harbison and others applied the.so-called taxonomic method while Adelman and Morris relied on factor analysis. Both · of these pioneering studies succeeeded in distinguishing socio­ politico-economic factors significant and insignificant for development. Although these attempts did not succeed in showing the causative rela- . tionships of sod-economic factors and in advancing explanatory models for development, they opened a new area of academic exploration and possibility for the future. 52. More recently, an attempt has been made by the national plan­ ning agency of Japan to relate socio-economic variables in a systems · dynamic modeI.38 The results of this attempt were not formally pub­ lished, but it represented a healthy effort to check if development poli­ cies were consistent with changes in the quality of life and well-being. There are also efforts to expand a traditional macro-economic model py introducing a number of structural equations using social indicators.39 The results of this effort are still a prototype experimentation requiring further tests · and verifications for practical application. Nevertheless, the study is an important beginning in the application of social indicators to development planning. · , E. CONCLUSIONS 
**Analysis**
The text discusses the application of social indicators in development planning, specifically in the context of economic development. It highlights the challenges of building models and the lack of statistical data, but also mentions pioneering works and recent attempts to relate socio-economic variables. This suggests that the text is focused on the intersection of economics and social sciences, which is a key aspect of economic development.

**Category**
Economic development, Education