الوفرة - الميزان الغــذائى
Food Balance Sheets
A food balance sheet presents a comprehensive picture of the pattern of a country's food supply during a specified reference period. The food balance sheet shows for each food item i.e. each primary commodity availablity for human consumption which corresponds to the sources of supply and its utilisation. The total quantity of foodstuffs produced in a country added to the total quantity imported and adjusted to any change in stocks that may have occurred since the beginning of the reference period gives the supply available during that period. On the utilisation side a distinction is made between the quantities exported, fed to livestock + used for seed, losses during storage and transportation, and food supplies available for human consumption. The per capita supply of each such food item available for human consumption is then obtained by dividing the respective quantity by the related data on the population actually partaking in it. Data on per capita food supplies are expressed in terms of quantity and by applying appropriate food composition factors for all primary and processed products also in terms of dietary energy value, protein and fat content.
- Supplies: The total quantity of foodstuffs produced in a country added to the total quantity imported and adjusted to any change in stocks that may have occurred since the beginning of the reference period gives the supply available during that period.
- Utilization: On the utilization side a distinction is made between the quantities exported, fed to livestock, used for seed, put to manufacture for food use and non-food uses, losses during storage and transportation, and food supplies available for human consumption.
- Per caput supply: The per caput supply of each such food item available for human consumption is then obtained by dividing the respective quantity by the related data on the population actually partaking of it. Data on per caput food supplies are expressed in terms of quantity and - by applying appropriate food composition factors for all primary and processed products - also in terms of caloric value and protein and fat content.
Annual food balance sheets tabulated regularly over a period of years will show the trends in the overall national food supply, disclose changes that may have taken place in the types of food consumed, i.e., the pattern of the diet, and reveal the extent to which the food supply of the country, as a whole, is adequate in relation to nutritional requirements.
By bringing together the larger part of the food and agricultural data in each country, food balance sheets also serve in the detailed examination and appraisal of the food and agricultural situation in a country. A comparison of the quantities of food available for human consumption with those imported will indicate the extent to which a country depends upon imports (import dependency ratio). The amount of food crops used for feeding livestock in relation to total crop production indicates the degree to which primary food resources are used to produce animal feed which is useful to know when analyzing livestock policies or patterns of agriculture. Data on per caput food supplies serve as a major element for the projection of food demand, together with other elements, such as income elasticity coefficients, projections of private consumption expenditure and of population.
It is important to note that the quantities of food available for human consumption, as estimated in the food balance sheet, relate simply to the quantities of food reaching the consumer. Waste on the farm and during distribution and processing is taken into consideration as an element in the food balance sheet.
Post-harvest losses in most of the countries are considered to be substantial due to the fact that most of the grain production is retained on the farm so as to provide sufficient quantities to last from one harvest to the next. Farm storage facilities in most of the developing countries are usually primitive and inadequately protected from wild animals and birds.
The losses tend to become even more serious in countries where the agricultural products reach the consumers in urban areas after passing through several marketing stages. In fact, one of the major causes of food waste in some developing countries is the lack of adequate marketing systems and organization. Much food remains unsold because of the imbalances of supply and demand. This is particularly true of perishable foods, such as fresh fruit and vegetables.
Technical losses occurring during the transformation of primary commodities into processed products are taken into account in the assessment of respective extraction/conversion rates.
However, the amount of food actually consumed may be lower than the quantity shown in the food balance sheet depending on the degree of losses of edible food and nutrients in the household, e.g. during storage, in preparation and cooking (which affect vitamins and minerals to a greater extent than they do calories, protein and fat), as plate-waste or quantities fed to domestic animals and pets, or thrown away.
Food balance sheets do not give any indication of the differences that may exist in the diet consumed by different population groups, e.g., different socio-economic groups, ecological zones and geographical areas within a country; neither do they provide information on seasonal variations in the total food supply. To obtain a complete picture, food consumption surveys showing the distribution of the national food supply at various times of the year among different groups of the population should be conducted. In fact, the two sets of data are complementary. There are commodities for which a production estimate could best be based on estimated consumption as obtained from food consumption surveys. On the other hand, there are commodities for which production, trade and utilization statistics could give a better nationwide consumption estimate than the data derived from food consumption surveys.
The food balance sheets presented here are standardized in that processed commodities are converted back to their primary equivalent- this is called "vertical standardization". The extraction rates or technical coefficients which were used in building up the database are used to carry out the conversion back to the primary level by multiplication of the reciprocal of the technical coefficient. For example, quantities of bread are expressed then in wheat equivalent and added to the originating commodity. So trade of wheat, in fact, includes wheat flour and wheat flour products in wheat equivalency. Furthermore, there is another standardization which one can label as "horizontal standardization". For example, where chicken meat, and turkey meat and other meats of the poultry family are shown separately in the detailed food balance sheet and aggregated as poultry meat in a single line in the standardized food balance sheet.
The reason for preparing standardized food balance sheets as opposed to detailed food balance sheets is firstly, to reduce the amount of data, and therefore the number of commodities involved, to a level and size more suited to analytical purposes. Such a reduction should take place without causing any significant loss of the basic variables monitoring the agricultural sector. Of course, dividing the calories for a given commodity in the standardized food balance sheet by the quantities shown as "Food" will not give the exact national or international nutritive factors that were used in the first place to calculate total calories since the "Food" is now a composite item in primary equivalent.
Secondly, preparing standardized food balance sheets and cancelling the intermediate production of derived commodities against the input use of primary products gives a clearer and more concise view of the availability of a product.
The accuracy of Food Balance Sheets
The accuracy of food balance sheets, which are in essence derived statistics, is of course dependent on the reliability of the underlying basic statistics of population, supply and utilization of foods and of their nutritive value. These vary a great deal between countries, both in terms of coverage as well as in accuracy. In fact, there are many gaps particularly in the statistics of utilization for non-food purposes, such as feed, seed and manufacture, as well as in those of farm, commercial and even government stocks. To overcome the former difficulty, estimates were prepared in FAO while the effect of the absence of statistics on stocks is considered to be reduced by preparing the food balance sheets as an average for a three-year period. But even the production and trade statistics on which the accuracy of food balance sheets depends most are, in many cases, subject to improvement through the organization of appropriate statistical field surveys. Furthermore, there are very few surveys so far known on which to base sound figures for waste, and in some cases also these are subject to significant margins of error. In most cases, the assumptions for waste used in food balance sheets are based on expert opinion obtained in the countries.
Given the limitations of available statistics , considerable use had to be made in the preparation of the food balance sheets of evaluation techniques provided by consistency checks. Internal consistency checks are inherent in the accounting technique of the food balance sheet itself. Even more important are external consistency checks based on related supplementary information, such as the results of surveys conducted in various parts of the world as well as relevant technical, nutritional and economic expertise.
It is believed that the food balance sheets as currently prepared, while often being far from satisfactory in s statistical terms, provide an approximate picture of the overall food situation of individual countries which may be used for economic and nutritional studies, the preparation of development plans and the formulation of related projects, as in fact are carried out in FAO.
The data evaluation and consistency checks that have so far been undertaken within the framework of the supply/utilization accounts for the preparation of food balance sheets in fact have revealed a number of gaps and inconsistencies in the underlying basic statistics for many, particularly developing, countries. Although these have been remedied by estimates and/or adjustments in the present food balance sheets for the purpose of providing a plausible picture of the food supply situation, the problems encountered should guide FAO s promotional and developmental efforts in the countries concerned to improve the coverage and quality of the basic statistics.