With few exceptions, birth rates are falling worldwide. What does this mean? Put simply, the fertility rate describes the average number of children a woman is expected to have over the course of her life, if exposed to the rates of a year. Therefore, women are having fewer children. But what about men? How many children do they have over the course of their lives? How does the male fertility rate differ from that of women? Researchers from the Max Planck Institute for Demographic Research, the United Nations Population Division, and the University of Oslo have investigated the development and future trends of gender-specific differences in fertility, e.g. in the total fertility rate, worldwide.
Henrik-Alexander Schubert, Thomas Spoorenberg, Christian Dudel and Vegard Skirbekk assessed the impact of population imbalances on male fertility using data from the UN World Population Prospects and indirect demographic-statistical methods.
"The key finding is that we are observing a shift from a higher total fertility rate among men to a higher total fertility rate among women, which has occurred globally in 2024. This shift is driven by an increase in the proportion of men in the population,' explains Schubert, a researcher at the MPIDR. Schubert and his colleagues attribute this to long-term trends such as falling mortality, narrowing mortality gaps between women and men, and the link to sex-selective abortions in some countries. Those trends sustain or exaggerate the male skewed sex ratio at birth throughout life.
The transition from higher male fertility to higher female fertility occurs at different points in time around the globe, and the timing is linked to the demographic transition. In the majority of European and North American countries, this crossover happened decades ago, mainly in the 1960s and 1970s. In most Latin American countries, the crossover happened in the recent past. By contrast, Oceania, South America and Asia have only recently undergone this transition. The cross-over from higher male total fertility rate to higher female total fertility rate is unlikely to occur before 2100 in sub-Saharan Africa, as the current decline in fertility has stalled and mortality remains high.
Differences in fertility between men and women are increasing as a result of the rising proportion of men in the population. These shifts present challenges for society, but also bring opportunities. Schubert comments: 'The challenges primarily affect men who remain childless — a status often associated with poorer health and growing dependence on professional care in old age. Urgent policy solutions are needed to counteract gender-specific differences in fertility and their consequences, such as childlessness among men.' The researchers propose three specific measures:
'If the challenges of these men are not taken into account, there is a risk of a cultural backlash against gender equality and social conflict,' warns the research team.
Proceedings of the National Academy of Sciences
People
Masculinization of populations reverses sex differences in fertility
20-Apr-2026