The largest census in history will be held in China July 1 this year.
''A nation of a billion people is holding a census . . . unprecedented in our history and in world history,'' said the official newspaper People's Daily Jan. 18.
Five million interviewers will fan out throughout China, armed with 19-item questionnaires. The interviewers, now being trained, will each have to reach about 200 people, or 40 to 50 families.
China has asked for United Nations assistance in preparing this census, the third since the establishment of the People's Republic of China in 1949.
The United Nations Fund for Population Activities has provided $15.6 million worth of assistance, and the UN Department of Technical Cooperation for Development is sharing its experience gained in census-taking all over the world.
Effective census-taking will depend heavily on the cooperation of the entire population, from densely inhabited metropolitan areas like Shanghai to the deserts of Inner Mongolia.
For the first time computers will be used in the census work.
The UN's major contribution is the supplying of 21 computers, including the central computer in Peking. Eight have arrived already. Licensing procedures required by COCOM, the 16-nation coordinating committee regulating sales of strategic items to communist countries, caused a long delay, but the logjam was broken late last year. International Business Machines is supplying the computers.
China has 21 provinces, five autonomous regions, and three independent municipalities. Each will require a computer. Besides the UN-supplied computers, China has purchased eight computers with its own funds.
The information assembled by the 5 million interviewers will have to be processed by 200,000 coders and 3,000 key operators. The work will probably take a year to complete, and final results may not be available until about two years later.
According to the state family planning commission, by the end of 1980 the population of China (not including Taiwan) had reached 982.55 million. The population increase that year was 8.97 million, about 10 per thousand, which is the lowest rate since the founding of the People's Republic. If this rate continues, the 1982 census will show China's population as slightly under 1 billion.
In a sense this is a success for the government's energetic one-child-per-couple movement. But as an article by Li Shiyi in the Peking Review of Jan. 11 points out, the population boom of the 1950s and '60s means that by 1980 there were 122.5 million women of reproductive age, whose average birth rate was 2.3 babies.
''If this rate continues unchecked,'' the article says, ''China's population will rise to 1.28 billion by the end of this century, and 100 years from now, it will exceed 2.5 billion.
''Since half of the present population is under the age of 20, they will progressively come of marriageable age as the century draws to a close, resulting in a new baby boom.''
Thus one result of the census will be to give an even greater sense of urgency to the government's family planning program.