| SYMBOLS AND UNITS | |
| ha | hectare |
| kg | kilogram |
| $ | US dollar |
| tonne | metric ton (1000 kilograms) |
| billion | thousand million |
| p.a. | per annum |
| calories | kilocalories (kcal) |
| TIME PERIODS | |
| 1990 | calendar year |
| 1988/90 | average for the three years centred on 1989, except if specified otherwise |
| 1970-90 | period from 1970 to 1990 |
| 1988/90-2010 | period from the three year average 1988/90 to 2010 |
GROWTH RATES
Annual percentage growth rates for historical periods are computed from all the annual data of the period using the Ordinary Least Squares (OLS) method to estimate an exponential curve with time as the explanatory variable. The estimated coefficient of time is the annual growth rate. Annual growth rates for projection periods are compound growth rates calculated from values for the begin- and end-point of the period.
COUNTRIES AND COUNTRY GROUPS
The list of countries and the standard groups used in this book are shown in Appendix 1. In the text, the terms "ax-Centrally Planned Economies" (ex-CPEs), "Eastern Europe" and "Former USSR" are used to denote the countries formerly included in the group "Eastern Europe and USSR". The historical data and projections are presented for these groups, and in the Appendix for the countries under their former names, because at the time this study was being prepared the data available for the new countries were inadequate for a systematic analysis The term "All Other (or Other) Developed Countries" is used for the countries referred to formerly as "Developed Market Economies", comprising all the developed countries shown in Appendix 1, except the ex-CPEs.
The term "93 developing countries" denotes the 93 developing countries analysed individually in the study. The term "developing countries excluding China" refers to the same 93 countries minus China. The term "all developing countries" refers to the same 93 countries plus all the smaller developing countries not covered individually.
LAND DEFINITIONS
Arable area is the physical land area used for growing crops (both annual and perennial). In any given year, part of the arable area may not be cropped (fallow) or may be cropped more than once (double cropping). The area actually cropped and harvested in any given year is the harvested area. The harvested area expressed as a percentage of the arable area is the cropping intensity. Land with crop production potential consists of all land area which is at present arable or is potentially arable, i.e. is suitable for growing crops when developed (see Chapter 4).
DATA SOURCES
All data are derived from FAO sources unless specified otherwise.