later ln the year. Furthermore, groups nith limited effective purchasing power areparticutarly vulnerable to the possibility that market supplies are pre-empted in times of shortages by those r,rho are economically advantaged. Estirnates of undernutrition 265. A simple method to estimate the total number and proportion of undernourished people vrou td be to calculate the number subsisting at calorie intake levels below Chose considered critical for carrying out ninimum daily activity without serious impairment. l4inimum requirements vary among individuals, depending on activity' climate, sex anal body weight. 265. IdeaIIy' data are needed on the calorie intake and requirements of each individual in order to estimate the number of undarnourished. In a comprebensive study in Tunisia it was found that some households in all income classes suffered fron calorie deficiency. tlhile 19 per cent of a1l rural househol-ds were below theA/ 40 /5L9 English Page 119 critical calorie lntake lever, for the ronest two incone classes (containing 23 per cent of total populatlon) the proportlon exceeded 30 per cent and thelncldence of undernutrition generally shoned an inverse relationship r.rith incomeIevels. Undernutrition was associateal rrith large family size in each income class. 257. As data on individual calorie intake and requirements are not generarlyavairable, the number of undernourished i9 estimateal by forloring the methodologyused.in the Fourth world Food survey. Those nho have.calorie intake less thanI.2 Bt',lR (basaI metabolic rate) e/ ate considered as undernourished. Baseal on thi.scriterion, 436 million people were undernourished during the period 1974-1976 inthe 86 countries for which the necessary data lrere.available or 23 per cent oftheir total population (see table 42). [iost of the undernourished people -349 million - were ln the low-income countries, where 29 per cent of the population
**Analysis**
The text discusses the issue of undernutrition and its relationship with income levels, calorie intake, and family size. It also mentions the methodology used to estimate the number of undernourished people. The text seems to be focused on a specific aspect of human well-being, which is related to the economic development and health of a population.

**Category**
Health, Economic development