(c) To determine the types of data required , such as product descriptions, prices and statistical weights; (d) To construct military price indexes and purchasing-power parities. C. Nature, scope and purpose of the exercise 16. According to the Group’s interpretation of its mandate, the exercise which it has been requested to carry out is of a primarily technical-statistical nature. It involves the collection from participating countries of a relatively large number of carefully selected data on military products and prices together with detailed information on the countries’ military expenditures. This need for a certain amount of statistical data is clearly implied by the very nature of the exercise itself and the task that has been assigned to the Group. 17. The methods for the construction of price indexes are generally well known and widely applied. Some countries already construct their own military price indexes on a regular basis. A special facet of this part of the present exercise, however, is the attempt which is made to construct military price indexes, in a simplified manner, while applying the same method and very similar sets of data for all countries. Results obtained and experiences gained from such a procedure might be of special interest, as practical methods of intertemporal comparison would presumably be required in the context of international negotiations on lasting agreements to reduce military expenditures. 18. The purchasing-power-parity (PPP) concept, however, is generally much less known. Practical experience in the construction and implementation of PPPS iS of recent date and still relatively meagre. AS exchange rates for various reasons prove to be rather poor instruments for international economic comparisons, there has for some time been a growing interest in finding instruments that are better suited for such comparisons. Thus, international bodies, such as the United Nations International Comparison Project, the Economic Commission for Latin America 
**Analysis**
The text appears to be discussing a statistical exercise related to military expenditures and prices, aiming to construct price indexes and purchasing-power parities. The context suggests a focus on international comparisons and economic analysis, rather than a specific sector or activity. This leads me to hypothesize that the text is related to economic analysis, specifically international trade and economic development.

**Category**
International trade, Economic development