Life Expectancy

Life expectancy, one of the methods of numerical expression of mortality dependence on age, consisting of constructions that characterize how a given cohort, under the influence of mortality, gradually decreases in composition with age; in other words, it is a series of numbers showing how many persons from a given cohort or of a known age reach each subsequent year of life. The magnitudes of life expectancy for each age depend on the level of mortality in the ages preceding the given one. The number of survivors is therefore a visual and convenient expression for characterizing age-specific mortality and, consequently, for determining the sanitary condition of the population. These magnitudes also have essential scientific-practical significance for various planning constructions regarding the probable future number of the population of different ages - school-age children, conscription age, working age, etc. In matters of life insurance, tables of survivor numbers are one of the main bases for all insurance calculations. Survivor numbers are usually obtained in the construction of so-called mortality tables. In this case, one can proceed in two ways, applying either the direct method of obtaining survivor numbers or the indirect method. - With the direct method, one starts from the numbers of births during a known period of time, for example, in some calendar year; when subtracting from this number (the so-called generation of that year) the numbers of deaths from this generation at ages 0-1, 1-2, 2-3, etc. years in subsequent calendar years, the numbers surviving to exact ages 1, 2, 3, etc. years are obtained, with the understanding that, naturally, individual persons reach these ages not all at once, but gradually, throughout a whole year. The direct method of construction mentioned requires approximately a century of observation, during which it is necessary that changes in the size of the cohort being traced occur only under the influence of mortality and not depend on migrations. This last condition, applied to the data of any country or locality, makes the direct method practically difficult to implement, if not impossible. At the same time, the direct method, giving a picture of the conditions of L., i.e., the order of extinction of a real, actually observed generation, leads to results characterizing the course of development of mortality of individual age groups in the more or less distant past. Meanwhile, for practical administrative, insurance, and sanitary purposes, the main significance is attached to data on L. and age-specific mortality based on values determined by contemporary sanitary, economic, and social conditions, and not by conditions that existed many years ago. This is achieved by applying the indirect method of constructing L. magnitudes; with this method, by comparing numbers of deaths, distributed by age, with similarly distributed population numbers, the probabilities of surviving to each subsequent year of life are first determined. Then, as the initial mass of births, some round number (1,000, 10,000) is taken, and by successive multiplications by survival probabilities, the numbers surviving to individual ages (from this round number of births) are obtained. Thus, the survivor numbers obtained indirectly do not represent the magnitudes of life expectancy of a real, actually existing generation, but those magnitudes that would result if some hypothetical generation were placed in conditions of age-specific mortality, the same as the mortality during the period for which data on deaths are taken. This indirect method is predominantly used to obtain L. magnitudes. In connection with the significant differences in the level of age-specific mortality in different countries and localities, the L. magnitudes to individual ages also represent large differences. For example, in the following table, the numbers surviving to age 50 from 1,000 births are compared for different periods of time and for different localities. Countries England and Wales »

» Germany » Leningrad » » British India Bavaria .... European Russia Switzerland . Denmark . . Norway Sweden . France . Holland Years 1838-64 1920-22 1871-81 1924-26 1910-11 1920 1926-27 1901-10 1834-67 1896-97 1920-21 1916-20 1911-21 1916-20 1920-23 1900-09 Male sex 456 699 412 710 340 146 512 187 352 362 685 681 649 647 638 633 Female sex 473 742 452 739 456 257 607 197 384 387 720 703 689 680 681 657 To characterize L. in the USSR in the past and at the present time, L. magnitudes to individual ages for the male sex are given for Ukraine under the conditions of age-specific mortality of 1896-97 and 1925-26, and in Leningrad under the conditions of mortality of 1910-1911 and 1926-27; for comparison, values for Germany under the conditions of mortality of 1924-26 are shown (see table on next page). From the table it is seen that at the present time, thanks to the decrease in mortality, both in Ukraine and in Leningrad, the numbers surviving to all the ages given are greater than in the past time. At the same time, compared with Germany, the numbers surviving in Ukraine and Leningrad still appear significantly reduced. In the Russian zemstvo sanitary-statistical practice, for studying the sanitary condition of the population, data from military medical boards were used along with other materials. The number of survivors from 1,000 conscripts (men), born. To Ukraine Leningrad Germany 1« age 1> t 1924-26 ГГ. o *-o: 0 years. . 1,000 5 » 10 » 15 » 20 » 25 » 30 » 40 » 50 » 60 » 70 » o of conscription age. Among the various elements subject to study in these materials (physical development of conscripts, percentage rejected, etc.), there was also the determination of the so-called coefficient of L. to conscription age. In the last years before the world war, conscription applied to persons who had reached 20 years of age by January 1 of the conscription year. Multiplied by 1,000 or by 100, the ratio of the number of conscripts in a calendar year to the number of boys born in that calendar year x - 21 therefore represents a relative number, or coefficient of L. of male pre-conscription age, showing how many of 1,000 or 100 born boys survived to this age. Since information about the number of conscription age persons is timed to the moment of conscription, conducted at the end of the calendar year, the average conscription age approximately corresponded to some intermediate age between 21-22 years of life. At the present time in the USSR, conscription applies to persons who had reached 21 years of age by January 1 of the conscription year; the average conscription age at the present time approximately corresponds to some intermediate age between 22-23 years of life, and to obtain the coefficient of life expectancy to this age, the number of conscripts in year x should be related to the number of boys born in calendar year x-22. The coefficient of L. to conscription age represents the magnitude of L. to a known age, obtained by the direct method. Its accuracy for individual localities depends on the degree of migratory movement of the male population of the given locality up to age 20-21 and, above all, on whether all persons born in the given locality are conscripted in the place of their birth. In the former, pre-revolutionary time, this condition was largely observed for the peasant rural population, since the peasant population was usually registered in the place of their birth. The existing works on the question of life expectancy to conscription age, mostly by sanitary physicians of the Moscow provincial zemstvo (V. A. Levitsky, A. V. Molkov, G. I. Rostovtsev, N. I. Skatkin, A. I. Skibnevsky, N. D. Sokolov), are of considerable interest and illuminate a number of questions about the connection of L. to conscription age with the level of infant mortality, with the monthly distribution of births of conscripts, with the connection with living conditions, literacy, etc.