VITAL STATISTICS (Lat. vitalis, relating to life, from rita, life, from virere, to live). That branch of statistics which studies the growth and changes of population. The facts which it seeks to interpret are derived from two main sources, censuses and registration reports. Censuses give information regarding population at a certain day. and show the changes and growth of population only by com parison between the results of two or more censuses. Registration reports are obtained by tabulating the records of certain important events made at or near the time of their occur rence. The scope and accuracy of these registra tion reports vary greatly with time and place. They usually include deaths, marriages, and births, and sometimes divorces, with various sta tistical facts about each. The number of such occurrences is controlled mainly by the number of people in the community for which the report speaks. To exclude this, the most im portant cause of difference in the figures, it is usual to compute the average number of births, deaths, or marriages occurring in a fixed unit of time, usually a calendar year, and in a fixed unit of population, usually 1000. The result of such
a computation has been named a rate. The death rate means the average number of persons dying in a year to each 1000 of the population. The marriage rate and the birth rate have simi lar meanings, except that the first term of the ratio is the number of persons marrying or the number of children born, respectively. Rates of this class are sometime?, known as crude or simple rate: in distinction from refined or corrected rates in which the unit of population may be a group each of whom possesses certain speeilied characteristics. Thus death rates are computed for a specified age and six and occupation and race, both terms of the ratio being correspond ingly limited, as for example the death rate of negro married women between twenty-five and thirty-four years of age.
The main statistical facts regarding the popu lation being found under the heading STATisTics, the present artiele is eonfined to the statistical results derived from rates.