Vital Statistics

Population changes reflect the natural facts of life: births and deaths. Births, in turn, have long been largely governed by the mechanisms of family formation. Vital statistics are compilations of data on marriage, divorce, birth, and death. Births and deaths directly determine changes in the size of a population; marriages and divorces create and dissolve, respectively, the conditions under which most births occur. The surplus of births over deaths is called natural increase; under unfavorable demographic conditions, deaths may exceed births, in which case a natural decrease occurs.

Vital events constitute one of the components of population dynamics; the others are migration and, for a group like the Jews, adhesion and withdrawal. In a "closed" population, unaffected by migrations and by adhesions or withdrawals, the numerical evolution depends entirely on the balance of births and deaths. The natural increase (or decrease) is indeed of fundamental importance for the future of any population, but the migratory changes may counteract the vital balance for some time. For example, despite strong natural increase, there was probably no growth in the total number of Jews in Eastern Europe at the beginning of the 20th century because of extensive emigration, mostly to America. On the other hand, among Jewish populations in Central and Western Europe throughout the 20th century prevailing natural decrease was outweighed or at least compensated by a positive migratory balance.

The figures of vital events in any population are strongly affected by its age composition. In a population containing a very large proportion of young adults, as may be the case where there has been large immigration, birth figures may be high in spite of a modest level of fertility (for definition of this term, see measurement, below); on the other hand, under conditions of advanced aging frequently found at present in Jewish populations, actual death figures may be high even though the specific mortality in each age group is comparatively low. All these factors need to be considered in evaluating the causes and consequences of population trends. The age composition of a population at any specific time is itself the result of the demographic dynamics of preceding decades: unless migratory influences or adhesions/withdrawals were particularly conspicuous, it largely depends on past fertility. A prolonged decrease in births leads to the aging of a population. In the early phases of aging the proportion of children decreases while that of all adults, including the adults of procreative age, increases. This in turn tends to sustain the crude birth rate while deaths of children will be relatively fewer per 1,000 of the population (which may reduce the crude death rate especially if child mortality is still conspicuous). In later phases of aging, the proportion of elderly and old persons in the population grows, and consequently, the crude birth rate is depressed and the crude death rate rises. Age composition thus intervenes as both the consequence and the cause of the frequency of vital events in a population.