Note 19 — IV.—COMPARATIVE CHANCES OF LIFE IN DIFFERENT CLASSES OF THE COMMUNITY.

A brief explanation of the construction of tables of mortality may be desirable to prevent misapprehensions by those who are unacquainted with the nature of such evidence. If amongst 4481 who die each year, as at Leeds, it be found that altogether, man, woman, and child, they have lived 92,734 years, that number equally divided, without distinction of the old and young, gives 21 years as the average period of life. The variations of such average periods, as shown by the tables showing the mean periods of death of a whole population, are deemed the best test of its condition and progress. The tables of proportional mortality are such as those of Liverpool, where, out of 223,054 inhabitants, 7435 die; that is to say, one-thirtieth of the ascertained population are swept away every year. Such tables only serve, however, for remote comparison of the condition of different districts, for it will be perceived how large will be the different conditions of two communities having exactly the same proportions of mortality, but in one of which the deaths occur principally amongst the infant population, and the other in which they occur amongst the adults. Thus in all the parishes of Leeds, where the average age of deaths of all who die is 21 years, since the deaths occur chiefly at young ages amongst the labouring classes, the proportions of the population who die annually is only 1 in 37. The average age of death, or the average extent of life to every individual, may go on increasing, and yet the proportions who die remain the same. Hence it is that statistical returns of the proportions of death, which are so generally used, are fundamentally unstable as means of ascertaining the progressive sanitary condition of a population in different countries. The probabilities of life at different periods of life on which insurance companies act, are determined by tables of a different construction. To form a table of the probabilities of life at given periods, in 1000 cases say, the date of the birth in each case is ascertained, and observations are made of how many remain alive at the end of each year at the different periods of life. From the different ages at which that 1000 have died, it is held to be probable that every other 1000 persons similarly circumstanced will die. The observations on which tables of this description have been founded have generally been from mixed classes differently circumstanced, and no observations on a basis sufficiently large, that I am aware, have been made to determine the probabilities of life to any one class of workpeople, or to any one class of professional persons. The three tables of the proportions of deaths at different ages would be of little service to indicate the probability of life at different ages unless we could ascertain with exactness the precise numbers of the classes living from which the deaths have occurred. More than half the children of the working classes die, and only one-fifth of the children of the gentry die, before the fifth year of age; and after having attained that age, the probabilities of life of the labourer’s child might be greater than that of the child of the person of the superior classes; but though we have other evidence that the reverse is the case, we have not the evidence of well-constructed tables of the probability of life at different periods strictly applicable to that class. Though the proportions per cent. of those who die in the higher and in the lower classes approximate in the periods between 20 and 60 years of age, yet we know that the probabilities of life in each class at each period are widely different. The probable duration of life of a miner who had attained 40 years of age may not be, and we have reason to believe is not, half that of the agricultural labourer, not one-third that of a person of the higher ranks who had attained the same period.