The term “population register” was defined in 1969, in the publication entitled Methodology and Evaluation of Population Registers and Similar Systems (United Nations, 1969), as “an individualized data system, that is, a mechanism of continuous recording, and/or of coordinated linkage, of selected information pertaining to each member of the resident population of a country in such a way to provide the possibility of determining up-to-date information concerning the size and characteristics of that population at selected time intervals” (chap. I.A). Thus, the population register is the product of a continuous process, in which notifications of certain events, which may have been recorded originally in different administrative systems, are automatically linked to it on a current basis. The method and sources of updating should cover all changes so that the characteristics of individuals in the register remain current. Because of the nature of a population register, its organization, as well as its operation, should have a legal basis.
Basic characteristics that may be included in a population register are date and place of birth, sex, date and place of death, date of arrival/departure, citizenship(s) and marital status. Depending on the possibility of proper linking with other registers, much additional information may be added to the single record, such as language(s), ethnicity, educational attainment, parity, activity status and occupation. In order to be useful, any additional information must be kept up to date. If complete, population registers can produce data on both internal and international migration through the recording of changes of residence as well as the recording of international arrivals and departures.
It has to be stressed that the primary function of the population register is to provide reliable information for the administrative purposes of government, particularly for programme planning, budgeting and taxation. The registers are also useful in other administrative areas, such as establishing personal identification, voting, education and military service, social insurance and welfare, and for police and court reference. Register information is also utilized for issuing documents needed for the admission of children to nurseries, kindergartens and schools and the assignment of residents to health clinics (United Nations, 1991, para. 476).
The use of the population register for vital statistical purposes entails linking events to the pertinent population at risk. The timeliness of the updating of the population register and the accuracy of the information recorded therein are thus factors critical to the quality of the statistics to be computed. The continuous and intensive administrative use of registers is an important means of ensuring their quality, since the everyday use of those registers in the society can facilitate the detection of errors. If the statistical and administrative functions of the population register are separated, an efficient system must be put in place to ensure perfect synchronization. Further, excellent coordination with the national and/or local authorities owning the vital events registers and a reliable technical infrastructure, based on computerization, are then required. In cases, where concerns about intrusion into the private lives of persons and about confidentiality risks may be spreading among the public, action should be undertaken to demonstrate the advantages of the system. Only widespread acceptance by the population can transform the population register into a reliable statistical source.
At the minimum, a population register includes a list of individuals with whom the local and/or national administration(s) of the country need to communicate. Although the national population register may very well be a virtual entity based on the linkage of population registers established at the local level (decentralized system), the overall geographical coverage must be of the entire territory of the country. If this condition is not met, the national population register will not be an appropriate system for the production of statistical data for the country.
Statistics on population and vital events should refer to the usually resident population. While for administrative purposes it is certainly legitimate to include in the population register persons who are not usual residents of the country (e.g., citizens living abroad, temporary residents, etc.), for statistical purposes care must be taken to identify the correct population of reference, especially if the statistics are used for international purposes and comparisons. The term “resident population” may indeed reflect various concepts of population and hence may refer, e.g., to the legal or registered (resident) population. However, the right of stay in the country (determining the legal or de jure population) or the simple registration of persons (who then make up the registered population) should not be considered sufficient criteria for identifying the usually resident population for international statistical purposes. Appropriate efforts should be undertaken to identify the usually resident population.
It is not required that additional information be physically recorded in the population register. What is necessary is the coordinated linkage of the population register with any other register containing that information. These other registers may also be structured differently, for instance, they may have in their single records units other than individuals, or they may refer only to registers of subset(s) of the population, such as the employed, students and retirees. The more registers are linked, the higher the possibility that the timing of their updates may be a risk factor for the quality of the information. Care should be taken to synchronize the operation of updating across all registers concerned.
A great advantage of computing vital statistics from population registers is the possibility of calculating directly specific demographic rates with potentially no numerator-denominator bias. For instance, it could be possible to compute specific fertility rates for employed and/or immigrant women, parity progression ratios, life expectancy by educational attainment, indicators on mixed marriages by ethnic group/foreign background, divorce rates by socioeconomic class of the spouses, etc. This requires full matching between civil registration and population register data as well as the same level of detail of information in the two sources, meaning that the certificate of the event (birth, etc.) must contain the same topics—with the same classification—as those available in the population register. In general, the use of the population register provides a broader opportunity to correctly identify the population at risk of an event.