Why has low fertility become a polarized issue?

Most countries today have below-replacement fertility and the global population is projected to decline before the century's end. Potential consequences include fiscal challenges of an aging population, slower economic growth, and weakened kinship networks. Yet the policy response of demographers has been relatively muted compared to their more active role in promoting population control during periods of rapid growth. While substantive considerations help explain disagreement over whether low fertility is a problem, this paper examines how competing moral frameworks-rooted in Social Justice and Social Order-may also shape public and academic responses to low fertility. I begin with a historical comparison between the politics of population growth and today's debate about population decline and develop a framework linking moral orientations to different understandings of demographic change and appropriate policy responses. I then use large language models to analyze the moral framing of fertility research published in eight leading demographic journals from 1947 to 2025. While most article abstracts contained neither moral frame, among those that did, 83% employed a Social Justice frame and 17% a Social Order frame, with Social Justice framing becoming increasingly prominent over time. I conclude by arguing that the predominance of Social Justice orientations may contribute to the muted response to low fertility, given that efforts to increase fertility align more closely with Social Order concerns, and that recognizing the moral dimensions of demographic debates can facilitate more constructive engagement.