Illiteracy is the inability to read and write. A person is defined as illiterate if he cannot, with understanding, both read and write a short and simple statement on his everyday life; and as functionally illiterate if he cannot engage in all those activities in which literacy is required for the effective functioning of his group and community, and also for enabling him to continue to use reading, writing and calculation for his own and the community's development. Lack of such abilities prevents individuals from going about their daily activities in modern society, seeking suitable employment, or moving about normally with comprehension of the usual printed expressions and messages they encounter. Its consequences include inability to take up basic social services, fill in even simple forms, and understand traffic instructions or other danger signs.
Of the adult world population (aged 15 years and over) the number of illiterates in 1990 was 28% of total, or 965 million; in 1980 was 28.6% of total, or 814 million; compared with 32.9% of total, or 760 million in 1970; and 39.3%, or 735 million in 1960. The burden of illiteracy falls hardest on the poorest and most disadvantaged groups, landless rural peasants, and slum dwellers. Nearly two thirds of those who are illiterate are women and the percentage is increasing. Most of the 965 million adults who cannot read or write are in developing countries.
The absolute increase over the past decade has been of the order of 80 million, about the same figure as over the previous two decades taken together. But the tendency has been for the total of those who cannot read or write to grow much more slowly than the total of those who can. The proportion of illiterates in the total adult population has been shrinking gradually, even as their absolute number has increased. Four out of 10 adults were illiterate in the early 1950s; just over 3 out of 10 in 1970; fewer than 3 out of 10 in 1980. About 40% of the world population of 3.1 billion (namely 1.2 billion) were illiterate in 1962. By 1992, the percentage of illiterates had dropped to 25%, but since the world population had increased to 5.5 billion, the absolute number of illiterates had effectively increased to about 1.4 billion.
Illiteracy among younger adults is lower than among the adult population as a whole, the result of the recent expansion in primary schooling. Nevertheless, by 1980, 2 out of 10 young people were reaching the age of majority without having acquired even a rudimentary literacy. Past experience suggests that those who fail to learn the basic skills by the end of normal school age have limited prospects of acquiring them later as adults. They can be expected to form a sizeable, if diminishing, illiterate segment of the working-age population for the next 40 years or more, until at least the year 2020.
In developing countries, illiteracy is a major obstacle to sustainable development. At current rates of population and education growth, there will be more than 900 million illiterate people by the year 2000.
Countless altogether illiterate people have been masters of highly elaborate languages. The ability of an oral tradition to transmit great masses of verse for hundreds of years is proved and admitted. Education is no friend to this oral literature. Culture destroys it, sometimes with amazing rapidity. When a nation begins to read, what was once the possession of the folk as a whole becomes the heritage of the illiterate only, and soon, unless it is gathered up by the antiquary, vanishes altogether. It has been suggested that literacy was the principal factor causing the decline of the English village culture.