Timely and reliable statistical information is one of the most important building blocks for the formulation of sound development plans and of policies, aimed at improving the efficiency of production and distribution of food and agricultural products in countries, thereby raising their standards of living. A statistical framework consisting of a series of Supply/Utilization Accounts (SUAs) for food and agricultural commodities can be a powerful tool for making the best use of available statistical information in formulating plans for developing the agricultural sector. Establishing such a system will also help to pinpoint many inconsistencies in the statistical series, leading to a better recognition of the need to improve statistics on food and agriculture.

II. GENERAL DESCRIPTION OF SUPPLY/UTILIZATION ACCOUNTS

Increased involvement of government authorities concerned with assessment, monitoring and planning exercises in the field of agriculture and rural development has a significant impact on processing methods for the compilation and analysis of statistical data. It is no longer meaningful to deal with individual statistical series, such as those of production and trade, etc., separately. Although individual data series continue to be important, it is equally important to establish the links between them. It is necessary to deal with flows and matrices rather than with individual sets of data. The statistics of any single commodity have to be traced all the way from production and utilization to final consumption.

As a consequence of maintaining the data series in this integrated fashion, it is possible to compute a variety of derived statistics and indicators relating to food and agriculture in a consistent manner from the same central data storage. The core statistics of such a statistical framework are the SUAs for food and agricultural commodities. For each product, the SUA traces its supplies from production, imports and stocks to its utilization in different forms: addition to stocks, exports, animal feed, seed, processing for food and non-food purposes, waste (or losses), and as food available to the population.

SUA Equations

These elements can be inter-related in a number of balancing equations. The first equates the sum of the supply elements:
opening stocks + production + imports

with the sum of the utilization elements:
exports + feed + seed + waste + processing for food + food + other utilization + closing stocks.

The preparation of a balance of this kind presupposes that reliable and independent information is available for each of its elements. Alternatively, if no information is available for one of the elements, the residual will provide an estimate. In practice, however, the construction of balances of this type is rendered difficult by the absence of adequate information on opening and closing stocks. Experience shows, however, that information on changes in stocks is made more readily available than on their actual size. If a net decrease in stocks is defined as "from stocks" and

a net increase in stocks as "to stocks" the following two equations will be obtained:

i) from stocks + production + imports = exports + feed + seed + waste + processing for food + food + other utilization;

or:

ii) production + imports = exports + feed + seed + waste + processing for food + food + other utilization + to stocks.

The combination of production and imports with both increases and decreases in stocks results in a supply available for export and domestic utilization, where domestic utilization is defined as the sum of: feed + seed + waste + processing for food + food + other utilization.

Advantages and Uses of SUAs

The advantage of storing the commodity data in the form of SUAs is that they are internally consistent in the sense that each element of supply of a commodity matches the other and total supply matches total utilization. This system provides a check on the plausibility of statistical data supplied by various national and/or international agencies. It also provides a useful tool for choosing between alternative sources of data and a logical framework for estimating missing observations. Even so, every effort must be made to make the data consistent by adhering, as far as possible, to the same definitions, coverage, specifications, etc., of each commodity and each

element. In practice, this means taking care not to mix statistical data for paddy rice with those of milled rice, or groundnuts in shell with shelled groundnuts, or harvested production with marketed or commercial production. Since total supply equals total utilization, the accounts are in the form of balancing equations with the result that one element usually is considered as the remainder.

In addition to the requirements for the analysis of individual commodities, account has to be taken of the use of SUAs in the preparation of various derived statistical measures, e.g.:

i) Food balance sheets: These present a comprehensive picture of the pattern of a country's food supply. The per caput supply of each food item available for human consumption is obtained by dividing the respective quantity by the related data on the population partaking of it. Data on per caput food supplies are expressed in terms of quantity, calories, protein and fat.

ii) Index numbers of production, trade and supply: One of the most important indicators for reviewing agricultural progress, and one that is extensively used, is the series of index numbers of food and agricultural production (total and per caput). Similarly, trade index numbers can be calculated independently for value, volume and unit values as well as index numbers of food supply (total and per caput).

iii) Self-sufficiency ratios and import dependency ratios: These indicate the extent to which a country's supply of commodities and/or total food is derived from national production or originates from abroad.

Time Reference Period

Problems relating to the time reference period to be used in reporting production, one of the most important elements in the SUAs, are manifold. Several twelve-month periods, such as July/June, October/September, April/March, have been proposed and tested. However, none of these periods covered satisfactorily and uniformly the production of all agricultural commodities and their use in a country. It can be assumed that there is no single twelve-month period which is fully suitable for recording supply and utilization for all products. It was therefore felt that although the calendar year time reference period (January-December) might not be a completely satisfactory solution, its advantages would appear to outweigh its disadvantages. The application of a calendar year time reference period during which the bulk of the harvest takes place also helps in linking the agricultural statistics with those of the industrial and other sectors of the economy.

III. CONCEPTS AND DEFINITIONS USED IN SUAs

A. Commodity Coverage

The first step in implementing an integrated and coordinated system of SUAs for food and agricultural commodities is to draw up a list of relevant primary and processed commodities. The definition of a complete list of commodities presents virtually insurmountable difficulties - both conceptual and statistical. For practical purposes, therefore, a pragmatic list of commodities will have to be adopted. In drawing up such a list, countries may wish to keep in mind a general list of food and agricultural commodities.

While the degree of detail of food commodities is to a large extent dependent on the requirements of food balance sheet preparation, a great degree of detail is required for the proper choice of food composition factors for the purpose of nutritional analyses. As an example, this calls for specifying the proportions of hard and soft cheese from whole milk or from skim milk. Similarly, the caloric and nutrient content of wheat (and other cereals) depends on the extraction rate used, the variety (hard or soft) of wheat milled and on its water content.

Among the various criteria to be taken into account when setting-up a commodity list, choosing suitable reporting units deserve particular attention. The data should be expressed in common units in order to facilitate international comparisons and the metric system should be adopted whenever possible. Values and prices should be converted and expressed in terms of a suitable currency. Some statistics, however, should be expressed in units, such as human and animal populations.

B. Supply and Utilization Elements

Each SUA consists of a number of supply and utilization elements all relating to a specific reference period, usually a twelve-month period, or an average of several twelve-month periods, and a specified geographical area, usually a country. Among the various elements a distinction is made between those that are basic or essential, such as production, imports, exports and domestic use and those elements that are supporting or supplementary, such as number of animals slaughtered, harvested area or the seeding rate.

Generally, SUAs are constructed for primary crops, livestock and fish commodities up to the first stage of processing in the case of crops and to the second (and sometimes the third) stage of processing in the case of livestock and fish products. The reason for this restriction on the higher stages of processing is that it is difficult to obtain data for all the forms of processed products and even more difficult, perhaps impossible, to trace the components of processed composite products.

This simplified system of accounting works well, except for imports and exports of processed products. In such cases, imports are shown in a separate account under "imports" and then utilized as "food" whenever appropriate, to accommodate the net addition to the total supply (and the total food) available to the country in question. Similarly, if there were exports of, say, bread, sufficient quantities of wheat flour should be allocated to produce the bread that is exported, in turn decreasing the availability of wheat flour to the country. In both cases, the account for bread would be pertinent only to trade. Complete accounts for derived commodities are constructed whenever the availability of data permits it. In such cases, the products derived from primary commodities are linked to their parent or originating commodity by extraction rates and conversion factors.

As already mentioned, the basic equation of a SUA equates supply with utilization over a given period. Only the basic or essential elements of an account are used in the equation. In the pure form, the total supply is the sum of opening stocks, production and imports, and total utilization is the sum of exports, domestic utilization and closing stocks where domestic utilization is defined as the sum of feed, seed, waste, processing and direct food. Due to the lack of adequate data on opening and closing stocks, changes in stocks, which often are easier to obtain, can be used, i.e., production, imports and the withdrawal from stocks to calculate total supply and exports, domestic utilization and addition to stocks to calculate total utilization.

The typical SUA for crops is composed of the following major elements:

Supply Utilization
01 Opening stocks
02 Area sown
03 Area harvested
04 Yield
05 Production
06 Imports
07 Withdrawal from stocks
08 Addition to stocks
09 Exports
10 Feed
11 Seed
12 Waste
13 Processing for food
14 Food direct
15 Other utilization
16 Closing stocks

The SUA for livestock includes the following elements:
01 Stock numbers
02 Females in reproductive age
03 Females actually reproducing
04 Birth rate
05 Births
12 Natural losses
13 Animals slaughtered
17 Take-off rate

The accounts for derived commodities do not have the element 02, while elements 03 and 04 become, respectively, "input" and "extraction rate" in the case of crops. For livestock products, 03 is "animals slaughtered" or "milking animals" and 04 is "carcass weight" or "yield per animal". All other elements remain the same.

The account for primary fish commodities is composed of the following elements:
05 Production
06 Imports
09 Exports
10 Feed
11 Breed/bait
12 Waste
13 Processing
14 Food direct
15 Other utilization

while the accounts for fish commodities obtained after processing include the following additional elements:
01 Opening stocks
03 Inputs
04 Extraction rate
07 Withdrawal from stocks
08 Addition to stocks
16 Closing stocks.

C. Definition of SUA Elements: Crop Sector

(01) Opening stocks, (16) closing stocks, (07, 08) changes in stocks.

Data reported should refer to the quantities in stocks of the commodity under consideration available at the beginning and end of the reference period, irrespective of its origin, i.e. whether from domestic production or imports. In principle, this should include stocks held at all levels between the farm and the level at which final consumption of the commodity occurs. Thus stocks figures would include government stocks, stocks with manufacturers, importers, exporters, other wholesale and retail merchants, transport and storage enterprises and stocks on farms. In practice, the information available often relates only to stocks held by governments, and even this is not available for important commodities in a number of countries. In the preparation of SUAs, therefore, this element is often not used. On the other hand, information on changes in stocks is more readily available and therefore SUAs contain data on net withdrawals from and additions to stocks rather than on actual stocks levels.

In the absence of information on opening and closing stocks, changes in stocks are also used for shifting production from the reference period in which it is harvested to the period in which it is consumed, e.g., olives picked towards the end of the year are crushed immediately after harvest to avoid spoilage. Olive oil output, therefore, cannot enter consumption during the same year. In this case, allocations are made to stocks in the year when the bulk of the harvest occurs and from stocks in the subsequent year when most of the oil is consumed.

(02) Area sown. Data refer to the area on which sowing or planting has been carried out for the crop under consideration. It is usually net for temporary crops and gross for permanent crops. Net area differs from gross area insofar as the latter includes uncultivated patches, footpaths, ditches, headlands, shoulders, shelterbelts, etc. An immediate use of area sown in the system is the calculation of the quantity of seed to be allotted for sowing in the following year.

(03) Area harvested. Data refer to the area from which a crop is gathered. Area harvested, therefore, excludes the area from which, although sown or planted, there was no harvest due to damage, failure, etc. The considerations made under area sown above apply also for area harvested.

If the crop under consideration is harvested more than once during the year as a consequence of successive cropping (i.e., the same crop is sown or planted more than once in the same field during the year), the area is counted as many times as harvested. On the contrary, area harvested will be recorded only once in the case of successive gatherings of the crop during the year from the same standing crop.

(04) Yield. The data reported under this element represent, for crop products, the harvested production per unit of harvested area. In most cases, yield data are not recorded, but rather are obtained by dividing the data stored under the production element by those recorded under element "area harvested".

(05) Production. This is, in general, the most important element of supply. Data stored under this element must be carefully controlled and cross-checked.

Crop production data recorded in the SUAs refer to the actual harvested production from the field, or from orchards and gardens. Excluded are harvesting and threshing losses and that part of crop not harvested for any reason. Production, therefore, includes the quantities of the commodity sold in the market (marketed production) and the quantities consumed or used by the producers (auto-consumption).

In many countries, crop production data are obtained as a function of the estimated yield and the total area. When this method is employed, it is important to be sure the total area does not refer to sown or planted area which would supply the "biological production," but only to the area actually harvested during the year.

When the production data available refers to a production period falling into two successive calendar years and it is not possible to allocate the relative production to each of them, it is usual to refer production data to that year into which the bulk of the production falls.

With regard to processed crop products, the element "production" corresponds to the total output obtained from the processing of the commodity in question during the calendar year. The quantity includes the output of home processing and of manufacturing industries and traditional processing. Data refer to total net production, excluding processing losses, i.e., the ex-factory or ex-establishment weight. Account should also be taken of the quantities lost in home processing which, for certain products, are quite significant.

The element "input" shown in the SUAs for derived commodities refers to the quantity of the originating commodity or commodities required for the manufacture of the derived commodity in question. Usually, the amount entered under this element will correspond to the total amount, or part of it, entered at element 13, "processing", of the originating product.

Again in the SUAs for derived commodities, the element "extraction rate" refers to the conversion factor (or rate) applied to the input data to estimate production of the commodity in question. The rate then indicates the average national rate at which these commodities are converted from the original form into their processed form.

(06, 07) Imports, Exports. In principle, trade data cover all movements of the commodity in question into the country (imports) and out of it (exports), as well as of commodities derived therefrom and not separately included in the set of SUAs. These elements include commercial trade as derived from customs' statistics, as well as aid and donations received by countries whether under government plans or by private institutions. The problem of unrecorded trade, when evident, can often be solved by estimating the related quantities using reports of trading partners and of specialized institutions. With regard to the SUA system, it is essential that trade is reported following the same "system of trade" (general trade or special trade) for both imports and exports in order to avoid either overstating or underestimating any other utilization data. As a general rule, trade data refer to net weight, i.e., excluding the weight of the container.

A number of commodities are processed into food and feed items. There is a need, therefore, to identify the components of processed material exported in order to arrive at a correct picture of supplies of food and feed in a country during a specified time reference period.

(10) Feed. This comprises amounts of the commodity in question and of commodities derived therefrom which are not shown separately in the SUA system (but excluding by-products, such as bran and oilcakes) which are fed to livestock during the reference period, whether domestically produced or imported.

(11) Seed. Data include the amounts of the commodity set aside for sowing or planting (or generally for reproductive purposes, e.g., sugar cane planted, potatoes for seed, eggs for hatching, etc.) during the year, whether domestically produced or imported. Account should be taken of double or successive sowing or planting when it occurs. Whenever official data are not available, seed figures can be estimated as a percentage of production or by multiplying a seeding rate with the area under the crop of the subsequent year

The data on seed also should include the quantities necessary for sowing or planting the area relating to that part of crop products to be harvested green or used for fodder (e.g., green peas, green beans, maize for forage, rye grass, legumes for forage, cabbage for fodder, etc.), and for re-sowing, owing to natural disasters like winterkill, floods, etc. In the absence of official information on the utilization of seeds, these data are very often estimates on the basis of data relating to seed rate and the "area sown" of the following year. If no data for area sown is available, area harvested should enter in the computation.

(12) Waste. Amounts of the commodity lost through wastage (waste) during the year at all stages between farms and the household level in handling, storage and transport should be recorded as waste. Not included is the waste of the edible and inedible parts of the commodity which occurs after the commodity has entered the household. The quantities lost during processing are also not included under this element because they are implicitly considered in applying the extraction rate. Waste in distribution tends to be considerable in countries with hot, humid climates, inefficient transportation and inadequate storage or processing facilities. This applies to the more perishable foodstuffs, and especially to those which have to be transported or stored for long periods of time in tropical climates. Waste is usually calculated as a fixed percentage of availability, the latter being defined as production plus imports plus stock withdrawals.

(13) Processing. The quantities entering this element of the balancing equation concern food and feed products and refer to the amounts used for processing into other commodities which are part of the adopted list of commodities. Among the elements used for the processed products, one refers to the "input", i.e., quantities of the primary products being processed. This implies that whenever a quantity is entered under the element "processed" of a primary product, the same quantity will have to be entered into the element "input" of the related processed product or products; e.g., wheat processed quantity is also recorded as input to the flour of wheat and bran of wheat accounts.

It often occurs that a primary product contributes to the input of several processed commodities. In this case, the sum of the inputs of all these derived products will be equal to the quantity of the primary commodity assigned to the element "processed"; e.g., processing of fruits may be equal to the sums of the inputs to fruit juices, canned fruits, dried fruits, alcoholic beverages.

Several processed commodities may be derived from the combination of more than one commodity. This is the case of "compound commodities" e.g., "vegetables frozen". The input to these products are obtained from the sum of the whole, or part, of the quantity recorded in the element "processed" of the commodities utilized.

In compiling the SUAs of the primary commodities, quantities assigned to the element "processed" should therefore be consistent with inputs of all possible derived manufactured products.

(14) Food. Data here refer to the total amount of the commodity available as human food during the year. These data include the quantities available to the producers themselves (auto-consumption) and those sold at the retail level or otherwise consumed by the population considered in the SUA system.

Availability may be in the form of the commodity to which the account refers, or in a form resulting from further processing into a product not included in the SUA commodity list.

It is important to note that the amounts entered in the element "food" refer to the quantities of food available for human consumption.

Refuse, which refers to stems, seeds and other inedible parts of food products, is also part of the quantity entered in this element. It is accounted for by the food composition factors that are used to calculate the caloric value of foods and the other nutrient values.

Clearly, "food" is one of the most important elements in SUAs if not the most important. The practice used for estimating food supply as a residual should, however, be supplemented by comprehensive household food consumption surveys in order to provide a cross-check on food availability in a country.

(15) Other utilization. This element covers the quantities of the commodity used during the year for non-food/feed purposes either as such or in a processed form not further pursued in the adopted system; e.g., yarns, carpets, rubber products and in general quantities used in non-food/feed industries, including the pharmaceutical, clothing and tanning industries.

Figures relating to "other utilization" include also the consumption of the population not included in the country population, e.g., tourists and labourers of neighbouring countries working in the country when their numbers are significant. In addition, the element should cover pet food.

D. Definition of SUA Elements: Livestock Sector

National livestock herd.

The construction of SUAs for the livestock sector requires a particular set of elements. These include those relating to the national livestock herd as such. The commodity list includes all domestic animals, by species, raised on farms or in the wild yielding valuable products, including animals for draft purposes. The livestock herd account is maintained for the major species for which enumeration takes place in the country.

(01) Stocks. This element indicates the number of animals of the species to which the SUA refers that were present in the country at the time of enumeration. It includes animals raised either for draft purposes, or for meat and dairy production, or kept for breeding. Live animals raised in captivity for fur or skin, such as foxes, minks, etc., are not followed up by the system although trade in fur skins is reported. The enumeration to be chosen, when more than one survey is taken, is the one closest to the beginning of the calendar year. Livestock data are reported in number of heads.

(02) Females of reproducing age. Data reported under this element refer to all the females in reproductive age belonging to the species indicated at the beginning of the year.

(03) Females actually reproducing. This element reports the number of females which have had offspring during the year. For species which can have more than one offspring during the year (i.e., sheep, goats and pigs) the breeding female has to be included for each litter. This element does not apply to chickens, turkeys and other poultry. Data are reported in the same units as indicated for the element "stocks" (code 01).

(13) Slaughtered. The number of animals recorded under this element includes all the animals of the species which have been slaughtered in the country. Meat production, within the SUA framework, covers all animals of indigenous and foreign origin that were slaughtered within the national boundaries.

Products of the livestock sector. The products obtained from the livestock sector can be divided broadly between products derived from slaughtered animals, e.g., meat, offals, fats, hides and skins and products obtained from live animals, including milk, eggs, wool, honey. Certain livestock products have so many derived products that they may be considered as originating products themselves, e.g., meat and milk. Processing of cow milk may be equal to the sum of the inputs for butter, cheese, whole milk evaporated, whole milk condensed, cream, and dry skim milk if such manufactured products are produced in the country. The SUAs for derived products of the livestock sector are similar to those of crop-derived products described previously.

In the section that follows, concepts and definitions are provided for those elements not covered previously.

Meat

Among the products of slaughtered animals, meat is certainly the most important. The particular elements, in addition to those discussed earlier, included in these commodities are animals slaughtered, carcass weight and production.

(03) Slaughtered. These data represent the number of animals slaughtered and are obtained by transferring the information recorded under element "slaughtered" (code 13) of livestock herd account of the species to which the SUA refers. Data are expressed in units (head).

(04) Carcass weight. This element refers to the output of meat per unit of animal slaughtered. The carcass weight reported in the SUAs is, in general, the "dressed carcass weight" and is usually calculated by dividing production of meat (element 05) by the number of animals slaughtered (element 03). Carcass weight, like yield and extraction rate, makes a good tool for checking consistency between meat production and slaughterings. Carcass weight data generally are expressed in kilograms per animal.

(05) Production. Data on meat production adhere usually to the following concepts:

- Liveweight: the weight of the animal immediately before slaughter.
- Killed weight: the liveweight less the uncollected blood lost during slaughter.
- Dressed carcass weight: weight minus all parts - edible and inedible - that are removed in dressing the carcass.

Meat production data recorded in the SUAs refer to the concept of dressed carcass weight.

The concept of meat production changes with the coverage of production as follows:
- Production from slaughtered animals: all animals of indigenous and foreign origin, slaughtered within the national boundaries.
- Production from indigenous animals: indigenous animals slaughtered, plus the exported live animals of indigenous origin.
- Biological production or total indigenous production: indigenous animals slaughtered, plus the exported live animals of indigenous origin and net additions (plus/minus) to the stock during the reference period. If it is expressed in weight, this measure should take into consideration also the change in the total liveweight of all the animals.

Meat production data may refer either to commercial production (meat entering marketing channels), inspected production (from animals slaughtered under sanitary inspection) or total production (the total of the above-mentioned categories plus slaughter for personal consumption). Production data shown in the SUAs refer to total production.

Offals

Offals refer only to edible offals because inedible offals are not followed up by the SUA system. Edible offals include all edible parts falling from or removed in dressing the carcass of a slaughtered animal.

(03) Slaughtered. Similar to the meat accounts already discussed, data here represent the number of animals slaughtered transferred from the element "slaughtered" (code 13) of the livestock herd account to the SUA for the edible offals or the fats. Data are shown in units (head).

(04) Offals yield. Data included in this element represent the quantity of edible offal per unit of slaughtered animal. The yield is obtained by dividing the quantity of edible offals produced and recorded in the element "production" (code 05) by the number of animals slaughtered as per element "slaughtered" (code 03) of the SUA. The offals yield is expressed in kilograms (kgs.).

(05) Production. Production data of offals refer to the total quantity produced during the year. Data are reported either by national authorities, or by other sources, or may be calculated on the basis of a given share of the dressed carcass weight, i.e., the percentage entered in element 17 - percent of carcass weight (see below). This is multiplied by the meat production of the related animal species, representing the overall dressed carcass weight of the animals slaughtered during the year. Data generally are expressed in metric tons (MT) for all commodities.

(17) Percent of carcass weight. As mentioned previously, in lieu of providing the actual quantity of edible offals produced during the year, many national statistical offices prefer to indicate the share of the dressed carcass weight that represents the production of edible offals. Naturally, this percentage varies, according to animal species. It may also vary over time due to changes in the average weight of the animals slaughtered during the year. For example if, as a consequence of a shortage of feedstufs or for any other reason, young animals are slaughtered in large proportions, the share of offals would be higher. Carcass weight is calculated also when actual quantities of edible offals are provided to verify the consistency with the quantity of meat production.

Fats

The commodities "animal fats" by animal species (e.g., fat of cattle, fat of buffaloes, fat of sheep, etc.), are associated with edible offals. The elements dealt with in the preceding paragraphs therefore apply also for animal fats, and need not be repeated here.

The concept adopted in the SUAs refers to "slaughter fats", defined as edible and inedible unrendered fats which fall in the course of dressing the carcasses and are recovered from discarded and fallen animals. These include guts, sweepings, hide trimmings, etc. Butchering fats and processed fats, such as lard, tallow and fat of poultry rendered are dealt with separately being products obtained from further processing, similar to meat and processed products from crops.

Hides and skins

The fourth product obtained from slaughtering that is pursued by the SUAs is hides and skins. The particular elements relating to these commodities are described below.

(03) Slaughtered. For SUAs of hides and skins data for the element "slaughtered" (code 03) are simply transferred from the element "slaughtering" (code 13) of the livestock herd account of the same species. When hides and skins are also obtained from fallen animals, the data for this element includes the number of slaughtered animals as well as fallen animals. In all cases the number of hides and skins produced corresponds to the number of animals recorded under this element. The number of slaughtered animals is useful in the event the production of hides and skins must to be estimated. Data are expressed in units.

(04) Yield. These data are de facto the weight of a fresh hide or skin. When production data is not available, yield is often used to calculate it using the number of slaughtered animals as a basis. The information is expressed in kilograms per piece (kg./pc).

(05) Production. Data refer to the weight of the fresh hides and skins before any further processing. They include hides and skins removed from slaughtered animals and collected from fallen animals. In the absence of official information, the total weight of hides and skins production is obtained on the basis of the weight per hide or skin (yield) as applied to the number of hides and skins produced (often identical to the number of slaughtered animals). Production of fresh skin of pigs is generally not estimated because the dressed carcass weight of pigs includes the skin, which is either consumed as meat or wasted. Some countries, however, remove the pig skin from the carcass and report its production.

Milk

Fresh milk is considered one of the basic foodstuffs. Derived products of milk, whether at the first or at higher stages of processing, are handled in the SUA system similar to other derived products. The particular elements shown here, in addition to those described previously are: milking animals, yield, and production.

(03) Milking animals. Data reported in this element refer to the number of animals which have actually been milked during the reference period. If, for example, the entire production of milk of a cow is sucked by its calf, the cow is not considered a "milking animal". This concept is in relation to the concept of milk production (see element 05 below) which excludes the milk sucked by the young animal. When constructing SUAs for fresh milk, it is recommended that the average number of milking animals is reported. The data are expressed in units.

(04) Yield. Yield represents the average quantity of milk produced by a milking animal during the year. In most cases, yield data are not recorded but obtained by dividing the data stored under the "production" element by those recorded under element "milking animal". Data are shown in kilograms per animal (kg./an).

(05) Production. Production data for milk indicates the quantity milked i.e., net milk production during the year even if it is later fed to young animals. Data on milk production are expressed in metric tons.

Eggs

Due to the larger importance of hen eggs, a separate account is kept for them while eggs of all other poultry are recorded together in the commodity "eggs excluding hen eggs". The particular elements that make up the SUA of "eggs" follow.

(02) Population. Only those females kept primarily for egg production (improved layers) and which have laid eggs in the course of the year are recorded under this element. Data for laying hens are expressed in thousand units.

(04) Yield. Yield is the average number of eggs in terms of weight produced by a layer during the year. Egg yields generally are not obtained independently but by dividing the quantity of eggs produced by the number of laying birds. Yield data are recorded in kilograms per animal (kg./an.).

(05) Production. Data on egg production refer to the quantity of eggs in terms of weight, produced during the year by all layers, whether in the traditional or modern sectors. It includes hatching eggs and eggs wasted at the farm. Production data are expressed in metric tons (MT).

(11) For hatching. The data recorded under this element refer to the overall quantity of eggs, by weight, used for reproduction during the year. Information relating to the eggs for hatching is rarely available and usually must be estimated. The following method of estimation is suggested:

- number of domestic poultry slaughtered plus those exported live plus or minus stock changes (x)
- estimated number of chicks died of natural causes (y) estimated number of eggs which did not open (z)
- number of eggs used for hatching (H)

This method of estimation may be expressed as an equation: x + y + z = H. The sum (H) divided by the number of eggs produced gives the ratio of eggs for hatching which is then applied to the weight of eggs produced to express the quantity in weight. The quantity of eggs for hatching is then converted to metric tons (MT).

Wool

Another product of the livestock sector which is important for some economies is wool. Wool is obtained from live animals as well as from the skin of slaughtered sheep. The particular elements of this account are those defined below.

(03) Producing population. This element refers to the number of sheep sheared during the year. Even if the sheep are sheared more than once in the same year, they are counted only once because their average production would be approximately the same if sheared only once. Data for this element are recorded in units (heads).

(04) Yield. The wool yields refer to the average quantity of wool produced by a sheep. As with other commodities, these wool yield data are in most cases calculated by dividing production data by producing population. Yield data are shown in kilograms (kg.).

(05) Production. Data on production refer to quantity of wool produced in the country during the year. They cover sheep and lambs' wool obtained by shearing the live animal or by stripping the pelt of the dead animal, whether or not slaughtered, by fermentation or by appropriate chemical treatment. This concept includes greasy wool or fleece-washed, but exclude sheepskins in the wool and wool wastes. Production data are expressed in metric tons (MT).

E. Definition of SUA Elements: Other Livestock or Animal Products

A few other commodities which are derived either from live animals, or from animals which are slaughtered only to obtain their skin and for which only production and trade data are recorded, include the following:

- animal hair of low quality gathered during the moult or by shearing or stripping from pelts, such as coarse goat or other animal hair and hair of horses;
- fine animal hair including that obtained from kashmir, angora and Tibetan goats, alpaca, hair of camels, llama, muskrat, nutria, etc.;
- fur skins which cover precious undressed raw skins with the hair, fur or wool attached, including astrakhan, karakul, Persian lamb, broadtail and similar skins.

Also included here are cocoons, both reelable and unreelable. For these commodities only production and trade data are recorded. Silkworm cocoons suitable for reeling cover not only the cocoons of the mulberry feeding silkworm but also those from similar insects. Unreelable cocoons, which include also cocoons waste, are dealt with separately while raw silk is a derived product. Production data of the products mentioned above are recorded in metric tons (MT).

Honey and Beeswax

The livestock sector includes also apiculture and related products. Consequently, the SUA system includes beehives, honey and beeswax. The data on beehives include only those relating to the elements of stock and trade. Stock data refer to the average number of beehives in the country during the year. Stock data are reported in units (number). The quantity traded is also reported in units. The SUAs relating to honey and beeswax include all elements which, in addition to those defined earlier, include the following three:

(03) Producing population. Data refer to the number of beehives as recorded in the element "stocks" of the beehives account and expressed in units (number).

(04) Yield. Data on yield refer to the average quantity of honey or beeswax obtained from a beehive. Yields of honey and beeswax are recorded in kilograms (kg.).

(05) Production. Production figures of honey and beeswax refer to the total production obtained during the year. Data on honey include only natural honey in the comb and further processed centrifugally. Beeswax production refers to raw wax, included in natural combs, pressed, bleached or coloured. Production data for these items are expressed in metric tons (MT).

F. Definition of SUA Elements: Fishery Sector

The SUAs of the fishery sector also deal with primary fish commodities and derived/processed products. The elements for these accounts, although common to those of the crop and livestock sectors, are in some cases defined again because of their special meaning when applied in the SUAs for fishery commodities.

Primary fish

The elements comprising the SUAs for fishery products which need to be defined follow. Data for these elements are expressed in metric tons (MT).

(05) Production. Production refers to the nominal catch, i.e., the live-weight equivalent of the landings of the retained catch (part of the fish caught or killed during the fishing operations may be discarded overboard because it is undersized, unsaleable or undesirable to the fisherman; while another part may go unrecorded because it is utilized by the crew for its own consumption or is used as bait during fishing). The nominal catch is thus the net weight of the quantities retained and landed plus the weight of the losses due to dressing, handling and processing on board, and the loss of the fluid content.

(10 Feed. The feed element of the SUA refers to the quantity of the commodity fed to fish for aquaculture and mariculture purposes.

(11) Breed/Bait. Under this mixed element are recorded fish used either for breeding or, more frequently, used as bait for other types of fishing.

(12) Waste. Waste refers to losses accumulated during the year between the landing and retail stage, as a result of handling, storage and transport practices. It does not include the waste of edible and inedible parts of the commodity which occurs after the retail level.

(15) Other utilization. This element covers the multiplicity of non-food uses of the catch, ranging from withdrawals from market to utilization of the shells of molluscs for jewellery and the quantities of fish used for ornamental purposes.

Derived Fishery Products

The SUAs of derived fish products are composed of the following nine elements. Several of these elements were considered previously, but are defined again because they assume particular significance in the fishery sector. These data are expressed in metric tons (MT) except for extraction rates which are shown in kilograms per metric ton (kg./GMT).

(03) Input. This element refers to the quantities of raw fish and shellfish, expressed in nominal catch weight (i.e., in liveweight equivalent) which are processed (e.g., filleted) and preserved (e.g., curing, canning, freezing, etc.). This element is blank in the case of by-products such as oil and meals from offals.

(04) Extraction rate. The extraction rate expresses the percentage of the input retained after the processing operation has been carried out. When available, it reflects the rate prevailing among national industries.

(05) Output. This element refers to the net quantity of the finished product obtained after processing and preserving the raw product, whether nationally caught or cultured, or imported. The output includes products produced on-board factory ships, by land-based industries and by fishermen’s' families as a domestic "cottage- level" activity. It includes preserved and processed fishery commodities produced on-board domestic fish factory ships and fishing craft even when landed directly in foreign ports, though in such cases the quantities involved are also included in exports.

(06) Import quantity and (09) Export quantity. In accordance with the internationally recommended practice, fishery import statistics include fish caught by foreign fishing craft landed in domestic ports and export statistics include fish caught by domestic fishing craft landed directly in foreign ports.

(10) Feed. Data stored under this element refer to the quantities fed to hatchery fish and domestic pets in the case of a commodity that normally would be destined to human consumption, or which is utilized to produce compound feeds for livestock, pigs and poultry in the case of commodities generally used for feeding purposes.

(12) Waste. This refers to the amount of the commodity lost through wastage during the year between the end of the processing operation and the retail level through handling, storage and transport practices. It does not include losses of edible and inedible parts of the commodity which occur after the retail level.

(13) Processing. The processing element records the quantity of an already processed commodity (e.g., frozen fish) which is then processed further (e.g., canned).

(15) Other utilization. Quantities designated as "other utilization" are those used for purposes other than food or feed, including fertilizer, or in some processed form not further pursued in the adopted commodity system, such as those quantities used in the pharmaceutical and tanning industries.