Demography is the study of human populations, including size, structure, distribution over space, socioeconomic characteristics, households and families, migration, labor force, and vital processes (birth, death, formation and dissolution of marital, and other unions). A central feature of this study is the collection, compilation, and presentation of demographic statistics. The most important single instrument is the census, an effort to enumerate the number of inhabitants and, historically, often households and/or families. In recent centuries, more detail has been collected than simple counts, namely such information as age, sex, race, nativity, language, marital status, occupation, industry, fertility, mortality, income, residence, and family and household structure. Censuses may either be complete counts or statistical samples of the population. The other mainstay of demographic data gathering is the continuous registration of vital events (births, deaths, marriages, divorces, and sometimes migration). This has been achieved through the establishment of parochial (church) or civil systems for the collection of such events. In recent decades, a number of nations have developed population registration systems that simply keep a continuous record of demographic events. A census can be taken by enumerating the register at any point in time. These modes of record-keeping have been augmented by sample surveys, especially where the cost and difficulty of taking a census are large, such as in many developing nations. Surveys also provide a means to calculate vital rates via indirect methods of estimation. Other administrative instruments have been used to study populations, including tax lists, military muster and conscription rolls, budgetary surveys, wills and bequests, and insurance data.
1. Prestatistical Regimes
The ancient civilizations of Egypt, Babylon, China, Palestine, and Rome took censuses. These were used for administrative purposes, such as determining fiscal, labor service, and military obligations. Heads of households, males of military age, adult citizens, and taxpayers usually were counted. Women and children were often omitted. Few of these records survive. The Bible mentions several, including one of the Israelites at the time of the Exodus and one by King David around 1017 BC. Rome conducted its censuses for about 800 years, first counting citizens and property in Italy for tax and military purposes, and later extending this to the entire empire. Joseph and Mary traveled to Bethlehem in response to such a census. The ancient empires of China took periodic censuses, the first relatively accurate one being in AD 2. They counted ‘doors’ (households) and ‘mouths’ (persons). These counts have allowed us an approximate reconstruction of China’s population over the last 2,000 years. The Inca empire of ancient Peru is said to have taken censuses, but the quipu recording system has never been deciphered. Similarly, the pre-Columbian Mexicans are known to have collected tribute censuses, but no codices recording this have survived.
More recently, the Domesday Inquest of England by King William I in 1086 provides us with a population benchmark for England. Such periodic fiscal and administrative surveys have functioned as quasicensuses for demographic historians, other examples being the French hearth tax lists of 1328, the English poll tax list of 1377, and the English hearth tax returns of 1690.
In England, a parish registration system of baptisms, burials, and marriages was instituted in 1538 for the new Church of England. France began such a system piecemeal, but the registers appear to be of acceptable quality by about 1670. In 1563 the Council of Trent decreed that all Catholic countries should keep parish registers. Other European countries followed suit. Ancient China created a system of family registers that was adopted in Japan and made official in 1721. National totals were compiled from the registers in Japan every 6 years up to 1852. Korea also instituted the register system, and compilations were made with some frequency from 1395.
2. Demographic Regimes of the Eighteenth and Nineteenth Centuries
The modern regime of demographic data collection on a national basis had its origins in the Scandinavian countries (Sweden, Denmark, Norway, Iceland, and, at times, Finland). Parochial registers were begun in the seventeenth century, using the clergy of the national, Lutheran churches. In Sweden, registration was made compulsory in 1686, in Norway in 1685, in Denmark in 1645/46, and in Finland in 1628. Annual data on births, deaths, and marriages were not published, however, until the eighteenth century, beginning in 1735/36 for Norway, Denmark, and Sweden. These nations also created census-like results from these registers, but actual household enumerations of a modern type were undertaken in 1749 in Sweden and in 1769 in Denmark and Norway.
Although the Scandinavian nations were forerunners, censuses had been taken elsewhere on more local level. In New France and Acadia in North America, 16 enumerations were made between 1665 and 1754, and a comprehensive system of parish registration was set up from the onset of French colonization (1608). For the British colonies in America, no fewer than 124 censuses were undertaken between 1623 and 1776. Some parish registers were set up, particularly in New England. Several Italian principalities (e.g., Sicily, Naples) enumerated their populations in the seventeenth and eighteenth centuries.
Later in the eighteenth century, some European nations took irregular and often rather incomplete censuses, including Spain (1768/69, 1787, 1797) and Portugal (1768). Regular enumerations truly began with the United States, whose Federal Constitution (1788) mandated a decennial census for the apportionment of seats in the House of Representatives. The first census was taken in 1790, and since then 22 national censuses have been taken. A much more general trend to regular national-level enumerations began in the early to mid-nineteenth century, both for governmental and general scientific purposes. This required the improvement of the bureaucratic mechanisms for collecting, tabulating, and publishing the results. There was also an increase in the types and detail of the types of information collected. More detail by age and sex was taken, and information on economic activities (e.g., occupation, industry) was also collected. Special censuses of agricultural and manufacturing units came to accompany the population inquiries. Among the nations commencing or continuing such activities in the early nineteenth century were the United Kingdom (England and Wales (1801), Scotland (1801), Ireland (1821)), France (1801), the Netherlands (1816), Portugal (1801), Prussia (1816), Bavaria (1816), Switzerland (1837), and Belgium (1831). As new nations were created, they began data collection for the new consolidations of former states: the German Empire took its first census in 1871 and the new United Kingdom of Italy in the same year. As the century progressed other nations joined: Spain (1857), Serbia (1834), Greece (1856), Russia (1897), Romania (1899), Austria (1869), Hungary (1857). Overseas nations also began the process: Canada (1851), Japan (1872), New Zealand and parts of Australia (1851), and many of the new nations of Latin America (e.g., Argentina (1869), Brazil (1872)). For a number of these nations, early efforts at enumeration were only partly successful. Colonial authorities took censuses in various other areas, especially in the Caribbean and in Asia (e.g., India (1881)). Many of these enumerations were seriously incomplete. Africa was the least well measured (and remains so).
One important issue for the promotion of demographic data sources was the creation of national statistical offices. In many cases, statistical collection functions were distributed among a variety of venues. In the United States, the census initially was collected by a temporary agency created for each census. The United States Bureau of the Census did not attain permanent status until 1902. Many European nations had statistical offices responsible for the collection and publication of demographic data by the middle of the nineteenth century (e.g., Statistics Sweden in 1858), and some had created institutions for similar functions for colonial areas. Many national-level annual statistical yearbooks were being published by these offices by the 1870s and 1880s.
An important impetus in this direction was the creation of a series of international statistical congresses, the first being in 1853. A series of recommendations were made concerning the need for regular censuses meeting basic standards. These resolutions were modified and expanded in subsequent congresses and were reinforced by the creation of the International Statistical Institute (1853). This work was continued by such bodies as the International Labor Office (1920), the Committee of Statistical Experts of the League of Nations (1920), the Inter-American Statistical Institute (1940), the World Health Organization (1948), and the Population Division of the United Nations (1947).
Vital registration did not expand as quickly. The countries of Scandinavia, Britain, France, many German states, and other European nations had the advantage of existing parochial registration systems. Some results from these systems were aggregated and published, such as in Scandinavia and England, or as ‘Bills of Mortality’ elsewhere, These systems gradually were converted to civil registration and thus became the basis for modern vital statistics collection. France secularized its parish registration under the Napoleonic Code in 1804. England and Wales instituted civil registration in 1837 and commenced published tabulations in 1838, but the system was only likely reasonably complete by the 1860s. The United States, a forerunner in regular enumerations, was a laggard in vital registration. The process was left up to individual states and, consequently, was accomplished unevenly. The state of Massachusetts was the first to have statewide vital registration (1842), but a partial national Death Registration Area was not even set up until 1900 (with 10 states and the District of Columbia, covering about 25 percent of the population). A Birth Registration Area was not created until 1915, and the system did not cover the entire nation until 1933.
Canada experienced similar problems with provincial registration, and the system there was not complete until 1926. Although the German Empire immediately created an Imperial Statistical Office in 1871, the various state statistical offices were only able to furnish basic counts immediately. Deaths by age, sex, and cause were not available for the whole empire until 1901.
Additionally, many nations established controls of the movement of persons across their borders, especially in the late eighteenth and in the nineteenth centuries. The consequence was the collection of international migration statistics, especially about arrivals but subsequently (and partially) on departures too. For instance, the United States was a major recipient of European migrants before World War I and began collecting data on arrivals in 1819 but on departures only from 1906. Also, publication of details was often uneven.
3. The Twentieth Century
In the period 1855-64, 24 sovereign nations took population censuses, 17 of them in Europe. During 1895-1904, 44 nations or colonies took a census, 23 in Europe and seven in North America and the Caribbean, but also five in South America and seven in Asia and Oceania. This progress continued. For the period 1945-54, 65 nations or colonies took censuses (28 in Europe, 12 in North America and the Caribbean, eight in South America, 15 in Asia and Oceania, and two in Africa). At that point, basic population counts were available for about 80 percent of the estimated world population, though detail was much more limited. For example, population classified by single years of age and sex was reported for only about 46 percent of the estimated world population. By the end of the twentieth century, almost all of the 233 countries in the United Nations had taken a census within the last two decades of the century. In some cases, nations with advanced continuous population registers (which collect information on a wide variety of social and demographic events) have supplemented or replaced censuses with estimates from their registers (e.g., the Netherlands, Sweden, Norway, Denmark, Belgium).
In terms of vital statistics, only about 53 percent of the estimated world population was covered in 1955, varying from 98 percent in North America, 94 percent in Europe, 43 percent in Asia, to 37 percent in Africa. Many of the systems in developing countries seriously under-registered both births and deaths. Sample surveys, such as the recent Demographic and Health Surveys, have supplemented knowledge of vital processes in all regions. As of 1992, of the 48 countries in Europe, all but three very small entities were categorized by the United Nations as having complete birth and death registration. In contrast, only 13 of the 57 countries of Africa were classed as having complete registration of deaths and only 10 as having complete birth registration. For Asia the proportions were 20 out of 52 for birth registration and 18 for death registration. Of the 14 countries of South America, seven were listed with acceptable registration for both births and deaths. The United Nations standard is rather liberal: to be classified as complete a system must have achieved a coverage of at least 90 percent.
A considerable advance in the collection of mortality statistics was made in 1900 when a conference of the International Statistical Institute approved the first international list of causes of death (ICD-1). This has been revised a number of times since then and is now under the auspices of the World Health Organization; the revision being operated is the ninth [ICD-9 (1979)]. As medical and scientific knowledge has improved, there has been a movement away from symptomatic cause attribution and toward etiological, organic, and epidemiological diagnosis.
Overall, although there have been substantial changes in demographic data regimes, especially in the twentieth century, the world is far from having a reliable and complete coverage. Recent political and economic tendencies do not indicate that the situation will improve. Sample surveys and indirect estimation of vital rates based on census and survey data would seem to be the answer for the immediate future for many developing nations, particularly in sub-Saharan Africa.