The Demographic Demon
Anxiety over declining birth rates and changing population composition is increasingly shaping politics, but history teaches that demographic processes are far more complex than apocalyptic forecasts.
Israeli and global politics alike are conducted in the shadow of demographic anxiety. It is this that explains the rise of the far-right in Europe, the anti-democratic drift of the judges-pilots-civil servants coalition in Israel, and other phenomena. Before discussing the normative implications of this anxiety, it must be noted that the "demographic demon" is not so terrible. Most long-term forecasts are speculative. Contrary to popular discourse, history shows that demographic trends do not behave exponentially in the long term, and their rate of change is not constant either.
Some of the apocalypse scenarios are completely absurd. The first among them is that "humanity is exterminating itself" because of the ever-decreasing birth rate. The argument is that the total fertility rate in the world currently stands at about 2.2 children per woman—only slightly above the fertility threshold required to maintain a stable population size (the "replacement level")—but is in a constant downward trend. Therefore, assuming the trend continues, the total population will soon begin to shrink and will continue to do so until its extinction.
One of the flaws in this argument lies in the hidden assumption that it is possible to calculate the population growth rate as if all its components have a uniform fertility rate identical to the average. In truth, the average rate weights data of sub-populations that differ on an ethnic, geographic, or religious basis, possessing distinct characteristics. To know the population growth rate under these conditions, it must be divided into various groups, explicitly marking the fertility rate in each and the rate of transition of individuals from one group to another (the tool for this is called the "Leslie matrix"), applying this reproduction mechanism again and again.
It is easy to show that it is enough to have one group in the population whose fertility rate and intergenerational survival rate are stable and whose product exceeds the replacement level for the population to grow over time. Let us demonstrate: assume the population consists of two groups with a stable mortality rate—90% are "blue" people, whose fertility is 1.5 offspring per woman and whose generation length (average age of the mother at birth) is 33 years; and 10% are "green" people, whose fertility is 5 and whose generation length is 28 years. Assume that one-third of the greens become blue in each generation and 5% of the blues become green.
With a number of simplifying assumptions, it can be seen that although the current reproduction rate is only 1.85 (lower than the ~2.1 needed to maintain size), the population will grow in the long term because the proportion of greens will rise. In this example, the population will indeed shrink at first to about 90% of its size, but due to the change in composition, it will return to the same size and even continue to grow. Contrary to the deepest fears of the "blue" people, they will not disappear, although they will lose their dominance. Assuming this mechanism continues to operate to infinity, the share of the blues will tend toward approximately 45% and will not fall below it (the "eigenvector" of the matrix).
It is difficult to guess long-term trends in the world or in Israel, but it would be foolish to assume that the culture of population components that maintain unique characteristics will remain similar to their current culture. History teaches that the new civilization created with the change in the demographic mix carries many characteristics of the previous one and enriches it. Hellenistic culture is called "Greek" by the Sages (Chazal) for a good reason—although it relied on a different ethnic infrastructure, it preserved many characteristics of Greek culture and blended them with new eastern elements. In the first century BCE, when fertility among the senatorial elite and the equestrian class in Rome was below the replacement level, Rome remained firm thanks to massive immigration and natural increase among the lower classes, and its culture flourished. It is likely that Western culture will also change and be enriched, Israeli society will develop, and there is no need to prepare for the end of all flesh.
