A census is an enumeration of all the people of a nation or a registration region, a systematic and complete count of all who are living in specified places, usually on a specific date. The practice of conducting a periodic census began in Egypt in the
In democratic societies, one important purpose of the census is to obtain a precise count of the people in each electoral district who are eligible to vote. For this reason even the politicians who oppose government "interference" in people's lives usually support the census. However, many people in nations with a past history of totalitarianism resist attempts to gather detailed personal information that is routinely gathered elsewhere.
Like most modern democracies, the United States conducts a complete enumeration every ten years, under the auspices of the Bureau of the Census, which publishes detailed reports. Some nations, such as Canada, hold an interim census at the five-year interval between the decennial census, often on a random sample basis. The rationale for this is that the composition and locations of the population is changing so rapidly that accurate current information is required to maintain essential services.
Information for the census is gathered in most countries by enumerators who visit every dwelling, systematically recording the name, sex, and age of everyone living there. Much other information is often collected at the same time and put to various uses. This may include other details about individuals and families, including ethnic origins, language, occupation, and marital status. Occasionally the census includes questions on health conditions, particularly chronic conditions and permanent disabilities such as blindness. Other useful facts include details about dwellings. This may include the number of bedrooms (a measure of crowding when related to the number of occupants); facilities for cooking and safe storage of food; sanitation and access to hot water; number of cars owned or used; number of telephones; and ownership of appliances such as television sets and computers. Some of this information has public health significance, and some is in the category of socially useful data. Some people regard questions with this level as unduly intrusive, but most willingly cooperate when reassured that the information will be used only to compile statistics. In the United States, census enumerators have all taken an oath of secrecy, and they can be punished with fines or even imprisonment if they disclose the facts they gather to any unauthorized person.
In certain countries, illegal immigrants or others living outside of conventional society avoid enumeration by various means, causing census to underrepresent the population. In parts of the United States with appreciable numbers of illegal immigrants, the proportion missed in the census may reach 10 percent. Estimates of actual numbers can be based on unobtrusive measures and indirectly obtained information such as school attendance and hospital room recordings.
JOHN M. LAST