“The outlook on the future of lowest-low fertility based on our analyses clearly indicates that this pattern is unlikely to be a short-term phenomenon that will quickly disappear from the demographic landscape.”

Extreme experiences and historically unprecedented situations often provide a unique opportunity for scientists to study social phenomena and their emergence through the behavior of individuals, social interactions, and institutional contexts. In addition, it is the encounter with new trends, constituting a marked discontinuity to earlier and accustomed situations, that heightens the public awareness about otherwise unnoticed social patterns and developments. It is also the experience of breaks with earlier trends that frequently prompts policy or institutional changes, and in many instances these adaptations of policies and institutions had been perceived as impossible only a few years or even decades earlier. Our paper provides one of the first systematic and comprehensive studies of such an unprecedented situation: the emergence and persistence of lowest-low fertility in Europe during the 1990s. This decline of fertility levels in many Southern, Central, and Eastern European countries to historically low levels in the last decade had been unexpected by many professional or casual observers of contemporary fertility trends, and it constitutes a trend that is of foremost social, economic, and political relevance. In addition, understanding lowest-low fertility provides a considerable challenge for researchers engaged in the field. This is due to the fact that the explanation of lowest-low fertility requires a detailed investigation of the causes, determinants, and implications of fertility decline, and it demands a re-evaluation and extension of many methods and theories that have become part of the standard toolkit for analyzing contemporary fertility behavior.

The major contribution of our work is the systematic analyses of lowest-low fertility that emerged during the 1990s, along with providing new theoretical perspectives to investigate lowest-low fertility and a discussion of the new methodologies to measure and project low fertility trends.

The interest in this research was partially inspired by my living in East Germany, an area of very low levels of fertility. The absence of children on streets provided a striking testimony about recent trends toward low fertility, especially after the German reunification, which took place in October of 1990.

The current demographic trends in Europe with historically low fertility and a rapid aging of the population challenges virtually all aspects of European societies, including the viability of pension systems and related social programs, the sustainability of long-term economic growth, intergenerational equity, and the perception of national identities. The demography of lowest-low fertility will therefore be at the center of a broad range of research efforts that address the opportunities and constraints imposed by the demography of the 21^st century with few children and long lives. Despite the growing public awareness about these aspects, demographer's and related social scientist's understanding of contemporary changes in fertility behavior has been limited. The central thrust of our argument is that lowest-low fertility is due to the combination of five distinct demographic and behavioral factors. First, demographic distortions of period fertility measures, caused by the postponement of fertility and changes in the parity-composition of the population, reduce the level of period-fertility indicators below the associated level of cohort fertility. Second, economic and social changes have made the postponement of fertility and a low progression to additional children after the first child a rational response for individuals. Third, perpetuating mechanisms, and in particular social interaction processes affecting the timing of fertility, render the population response to these new socioeconomic conditions substantially larger than the direct individual responses. Modest or path-dependent socioeconomic changes can therefore lead to a rapid and persistent postponement transition from early to late age-patterns of fertility. Fourth, an institutional setting is in place that favors an overall low quantum of fertility. The outlook on the future of lowest-low fertility based on our analyses clearly indicates that this pattern is unlikely to be a short-term phenomenon that will quickly disappear from the demographic landscape. In our opinion, lowest-low fertility is likely to be a persistent pattern. We expect that it prevails for a considerable period in Southern, Central, and Eastern European countries with a total fertility rate below 1.3. In addition, we believe that lowest-low fertility is likely to spread in the near future to several other countries that currently experience a total fertility rate between 1.3 and 1.5. These "lowest-low fertility candidates" include Austria, Germany, along with several Central and Eastern European countries like Poland, Lithuania, Slovakia, Croatia, and also Asian countries like Korea and Japan.