DEMOGRAPHY, the science which deals with the statistics of health and disease, of the physical, intellectual, physiological and economical aspects of births, marriages and mortality (from Gr. oigor, people, and p6.0ety, to write). The first to employ the word was Achille Guillard in his Elements de statistique humaine ou demographie comparee (1855), but the meaning which he at tached to it was merely that of the science which treats of the con dition, general movement and progress of population in civilized countries; i.e., little more than what is comprised in the ordinary vital statistics, gleaned from census and registration reports. The word has come to have a much wider meaning and may now be defined as that branch of statistics which deals with the life-condi tions of peoples.