POPULATION (IH.. populatio, from popu lure, to populate, from Lat. populus, people; connected with plenus, full, and ultimately with Eng. full). The number of living human beings. This article will present the leading facts re garding the number of human beings and the number in various classes; reserving for the article VITAL STATISTICS the main facts regard ing the increase in the number of human beings. The distinction between population and vital sta tistics corresponds closely to the distinction be tween the main sources of information, namely, the census reports and registration reports. In census reports the element of time is either dis regarded or reduced to a minimum and an at tempt is made to photograph certain aspects of the population as they were on the census day.. Registration reports are records of certain de fined events within a population group, such as births and deaths, marriages and divorces, im migration and emigration, legal punishments for crimes, the record being made at or soon after the event recorded. Inferences regarding the increase of a population in time may be derived from comparing a series of censuses; but the census cannot give the detailed information about increase or decrease derivable from registration reports.
The population is ascertained by many methods of different degrees of accuracy. Houses are counted and multiplied by the estimated number of persons to a house. The population of school
age or the number of names in a city directory is counted and the result multiplied by a num ber representing the ratio that the class is be lieved to bear to the total population. But in most eases such methods result in great uncer tainty and error, and have gradually been super seded in civilized countries by the slow, expen sive, but far more accurate method of a complete count or census. At the present time two thirds of the population of the earth has been thus counted. The extension of repre sentative institutions has necessarily extended the census as an accurate means of counting population, for under a representative system political power is distributed in some measure according to numbers. It is not surprising. therefore, that the United States, as a great modern country with representative institu tions, was the first to count its population by a census.
The population of the earth's surface at the beginning of the twentieth century was probably about 1.500,000,000. About nine-tenths of this population is included within the jurisdiction of eleven of the principal States of the world. The distribution in round numbers is as follows, the figures embracing all colonial possessions and dependencies of every kind (some merely nom inal) :