36. The nature of a PPP can be illustrated by the following example. If expenditures on doctors are $10,000 per day for country A,and 30,000 francs per day for country B, and the rate of exchange between the dollar and the franc is set at six francs to one dollar, then country 8, according to this method of comparison, spends $5,000 for this service, or half of what country A spends. If the aim is to measure the quantity of services the two countries procure for their respective expenditures (assuming that the doctors of both countries have the same productivity), the number of doctors of the two countries accounting for corresponding expenditures can be taken as conversion factors. If country A has 5,000 doctors and country B has 4,000 doctors, the PPP can be calculated as follows: (10,000/5,000)/(30,000/4,000) = $US 0.267 dollar for 1 franc, which equals 3.75 francs for $US 1. 37. If it is known that the average price of a sample of doctors is respectively $15 and 45 francs per hour, and if these prices are used as a criterion for calculating the purchasing-power parity of doctors, the result is 3 francs for $1. Thus, starting from.each of our three hypotheses, we obtain three indexes for converting francs into dollars, which diverge by as much as 6 to 3. If, in compar ing mi li tary expenditures, it is decided to set aside the rates of exchange, there remain the methods based on prices or quantities. Calculations based on: (4 Exchange rates i (b) (cl Average prices derived from expenditures Sampled relative and quantities prices 6 francs per 3.75 francs per dollar dollar 3 francs per dollar 38. The purchasing-power parity method is designed so as to avoid the kind of 
**Analysis**
The text discusses the concept of Purchasing Power Parity (PPP) and its application in comparing expenditures between two countries. It presents different methods for calculating PPP, including exchange rates, average prices, and quantities. The text does not seem to be related to economic development, natural resources, agriculture, forestry, fishing, industry, transport, communication, humanitarian aid, culture, or science and technology. It appears to be more focused on economic issues, specifically international trade and finance.

**Category**
International trade