Technical notes

Calculation of average annual growth rates

Agricultural sector

The growth rate, r (expressed as a percentage), is calculated between two time points  using the following formula:

where p_n and p₁ are the last and first observations in the period respectively, n is the number of years in the period, and ln is the natural logarithm operator.

Macro Economic Aggregates

The growth rate for the macro economic aggregates (GDP and Agricultural GDP) is calculated by fitting a linear trend line, of the form

lnX_t = a + bt

to the annual values in the time series corresponding to the aggregate X. The parameter b is estimated by the least-squares method and the growth rate, r (expressed as a percentage), is then derived as follows:

Population and labour force estimates

The population and labour force estimates presented in these tables are based on the products of a coordinated inter-agency work programme involving the UN Population Division, the ILO Bureau of Statistics and the FAO Statistics Division.

The basic framework for the set of demographic estimates is the estimates of the total population by sex and age, which are prepared by the UN Population Division. The estimates of urban/rural population, economically active population (labour force) and the agricultural population are obtained by systematically applying estimates and projections of the relevant population ratios (i.e. the proportion of urban/ rural population, the activity rates by sex and age and the proportion of agricultural population)   to the total population. The economically active population in agriculture (agricultural labour force) is obtained by applying estimates of the proportion of economically active population in agriculture to the total economically active population.

The estimates of the total population are biennially revised by the UN Population Division and the figures in the present document are based on the 2002 revision (“World Population Prospects: The 2002 Revision”, United Nations, New York, 2003). The estimates of the proportion of urban/rural population, which are also prepared by the UN Population Division, refer to the assessment made in 2001 (“World Urbanisation Prospects: The 2001 Revision”, United Nations, New York, 2002). The estimates of the activity rates by sex and age, which are produced by the ILO Bureau of Statistics, are based on the assessment made in 1996 (“Economically Active Population, 1950 – 2010”, Fourth Edition, ILO, Geneva, 1996). The estimates of the proportion of the economically active population in agriculture also emanate from the latter assessment while the projections were prepared by FAO Statistics Division (“World-wide Estimates and Projections of Agricultural Population and Labour Force”, FAO, Rome, 2000).

Population Density

 Total population divided by land area.

Food production indices

 The FAO indices of food/agricultural production show the relative level of the aggregate volume of food/agricultural production for each year in comparison with the base period 1999-2001. They are based on the sum of price-weighted quantities of different food/agricultural commodities produced after deductions of quantities used as seed and feed weighted in a similar manner. The resulting aggregate represents, therefore, disposable production for any use except as seed and feed.

All the indices at the country, regional and world levels are calculated by the Laspeyres formula. Production quantities of each commodity are weighted by 1999-2001 average international commodity prices and summed for each year. To obtain the index, the aggregate for a given year is divided by the average aggregate for the base period 1999-2001.

Since the FAO indices are based on the concept of agriculture as a single enterprise, amounts of seed and feed are subtracted from the production data to avoid double counting them, once in the production data and once with the crops or livestock produced from them. Deductions for seed (in the case of eggs, for hatching) and for livestock and poultry feed apply to both domestically produced and imported commodities. They cover primary agricultural products used as such (e.g. maize, potatoes, etc.).

The “international commodity prices” are used in order to avoid the use of exchange rates for obtaining continental and world aggregates, and also to improve and facilitate international comparative analysis of productivity at the national level. These ”international commodity prices”, expressed in so-called ”international dollars”, are derived by using the Geary-Khamis formula for the agricultural sector. This method assigns a single “price” to each commodity. For example, one metric ton of wheat has the same price regardless of the country where it was produced. The currency unit in which the prices are expressed has no influence on the indices published.

The commodities covered in the computation of indices of food/agricultural productions are all crops and livestock products originating in each country. Practically all products are covered, with the main exception of fodder crops. The category of food production includes commodities that are considered edible and that contain nutrients. Accordingly, coffee and tea are excluded along with inedible commodities because, although edible, they have practically no nutritive value.

Indices for meat production are computed based on data for production from indigenous animals, which takes account of the meat equivalent of exported live animals but excludes the meat equivalent of imported live animals. For index purposes, annual changes in livestock and poultry numbers or in their average live weight are not taken into account.

The indices are calculated from production data presented on a calendar year basis.

The FAO indices may differ from those produced by the countries themselves because of differences in concepts of production, coverage, weights, time reference of data and methods of calculation.

Food Balance Sheets (FBS)

The FBS are compiled every year by FAO with country-level data on the production and trade of food commodities. Using these data and the available information on seed rates, waste coefficients, stock changes and types of utilization (feed, food, other uses), a supply/utilization account is prepared for each commodity in weight terms.

The food component of the commodity account, which is usually derived as a balancing item, refers to the total amount of the commodity available for human consumption during the year. Besides commodity-by-commodity information, the FAO FBS also provide total food availability estimates by aggregating the food component of all commodities including fishery products after conversion into nutritive values. From these values and the available population estimates, the per caput dietary energy and protein and fat supplies are derived and expressed on a daily basis.