According to the most recent UN estimates (United Nations 2017), almost one half of the world’s population lives in countries with below replacement fertility (BRF), i.e. with a total fertility rate (TFR) below 2.1 births per woman. Of these, one quarter have TFRs close to the replacement level, i.e. between 1.8 and 2.1; the other three-quarters have really low fertility, below 1.8 births per woman. Low-fertility countries are generally grouped into clusters. The main clusters are in East Asia, Southern Europe, the German-speaking countries of Western Europe, and all the former socialist countries of Central and Eastern Europe (Table 1). In fact, contemporary fertility around the globe is lower than it has ever been. Since the middle of the 20 th century, childbearing has declined by 50 percent: 50 to 60 years ago women in developed and developing countries combined had on average 5 children, but now the world […]